US20120165158A1

US20120165158A1 - Wearable and convertible passive and active movement training robot: apparatus and method

Info

Publication number: US20120165158A1
Application number: US13/326,317
Authority: US
Inventors: Yupeng Ren; Li-Qun Zhang
Original assignee: REHABTEK LLC
Current assignee: REHABTEK LLC
Priority date: 2010-12-14
Filing date: 2011-12-14
Publication date: 2012-06-28
Also published as: CN102614066B; CN102614066A

Abstract

In respects of limitations and problems of motor function training devices, the present invention provides a wearable and convertible device and a method for controlling combined motor function training. This device integrates the functions of both passive stretching function in the existing CPM devices and additional active assistive training function. Without a force/torque sensor element in the device, the present passive stretching control can still be adapted to hypertonia (high muscle tone or stiffness of joints) of the limb, and the present active assistive control can still be implemented for enhancing voluntary active movement from patients. With such present method, much more applications of active assistive training are supported at substantially no additional cost. On the other hand, the safety of such stretching devices without using force/torque sensor is improved, which assists in increasing the efficiency of the device of the present invention.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention generally relates to a motor function training device for upper or lower extremity of people with neurological disorders or musculoskeletal injuries. This invention presents a simplified mechanical structure of wearable and convertible with a novel control method to conduct safe and effective joint stretching and active assistive guidance functions without using additional torque/force sensor.
2. Description of Related Art
Joint mechanical properties and movement control are important in functional activities and they may be affected in neurological disorders and musculoskeletal injuries, such as reduction in joint range of motion, increased stiffness, increased muscle tone, and impaired motor control. And neurological impairments, including stroke, spinal cord injury, multiple sclerosis and cerebral palsy are the leading causes of motor dysfunction. Brain damage caused by spasticity and contracture will result in lasting effects in patients. The hypertonus and reflex hyperexcitability disrupt the remaining functional use of muscles, impede the limb movement, and also cause severe pain. Prolonged spasticity, usually accompanied by muscle fibers and connective tissue changes in the structure, may lead to further reduction in joint range of motion. The present invention aims to solve clinical rehabilitation-related training issues such as contractures, spasticity, muscle weakness and motor control problems.
Current Clinical Problems:
1) Typically, physical therapists uses physical modalities and physical manipulation of a patient's body with the intent of reducing spasticity and contracture, thereby restoring the patient's balance, coordination, and motor function. However, the manual stretching is strenuous and the outcome is dependent on the experience and the subjunctive “end feeling” of the therapists.
2) Without assistance of any rehabilitation device or physical therapist, the patient may have difficulties to achieve or remain an active body movement continuously and stably and cause a delayed process of fully motor function recovery. Furthermore, they could experience further joint injury due to lack of knowledge of rehabilitation or over excessive rehabilitation
3) Due to the shortage of therapist resources, patient may only receive limited infrequent therapy and the therapy effects may not be long-lasting. Therefore, for both patients and therapists, there is a need for a simplified, portable rehabilitation device that can stretch and mobilize the joint accurately, reliably and effectively.
4) Training and exercise is important in neuroplasticity and motor recovery post stroke [1]. The most recent Clinical Practice Guidelines [2] “recommend that rehabilitation therapy start as early as possible, once medical stability is achieved.” Considering that early onset of rehabilitation interventions is strongly associated with improved functional outcome [3], the proposed intervention is related to a wearable and convertible rehabilitation device to help people be able to get out of bed and be mobile as soon and as much as possible. It can guide impairment-specific rehabilitation in an early stage.
Limitations of Existing Technologies and Inventions:
Related Passive Stretching
Passive stretching of spastic/contractured joints has been used extensively by therapists with beneficial results [4-12]. A number of devices have been developed for passive stretching. Serial casting which fixes the limb at a corrected position has been used to treat ankle contracture. Combining serial casting with manual stretching is usually a more effective treatment for correcting ankle contracture [13]. Dynamic splinting and traction apply a continuous stretch to the joint involved through an adjustable spring mechanism [14]. Motorized/robotic devices have also been used to move stiff joints passively to increase joint ROM and reduce joint stiffness. For example, the CPM is widely used in clinics and in the patient's home to move a joint within a pre-specified movement range, to reduce joint stiffness and to prevent postoperative adhesion [15]. Loosening up stiff muscles/joints in the impaired limb may help the CNS command to control the muscles and move the joint properly. CPM has also been used in treating patients acutely post stroke [16-19]. Lynch et al. used a shoulder CPM to treat the paretic arm of acute patients post stroke and found that CPM-treated patients showed positive trends towards improved shoulder joint stability when compared with patients performing therapist-supervised self-range of motion [16].
However, existing devices like the CPM machine move the limb at a constant speed between two preset joint positions. When it is set within the flexile part of the joint ROM, the passive movement does not usually stretch into the extreme positions where hypertonia/deformity is significant, especially in chronic patients who develop more significant hypertonia/deformity over time. On the other hand, setting a CPM machine too aggressively may risk injuring the joint because the machine controls the joint position or velocity without incorporating the resistance torque generated by the soft tissues. In the above study [16], for example, CPM was used in such a way that extreme positions of the shoulder range of motion were avoided for safety reasons.
Related Active Assistive Training with Robot Assistance
Many assistive training devices have been developed in recent years to help improve voluntary control and motor recovery of the upper limb after stroke and other neurological impairments [20-28]. Practically, advanced rehabilitation robots are too expensive for local clinic and home uses. Functionally, rehabilitation robots often focus on active assistive movement training and do not provide integrated passive and active movement therapy. By using an additional force or torque sensor, such active assistive movement training device can precisely measure both the joint resistance caused by spasticity and contracture and active movement intention. By using specific control methods, the devices can provide assistive guidance accordingly to help patients move to a target position or follow the free limb movement. However, the implementation of system function and control is dependent on the precision of an additional force or torque sensor, which increases the system cost and makes it not suitable for a wide range of clinical and home use. Functionally, such rehabilitation training devices only focus on active assistive movement training and exclude effective passive stretching function due to the limitation of the mechanical structure.
For many conventional robotic devices, a torque/force sensor is required in the system control programs. In this present invention, a mechanical structure and a novel control method do not require a torque/force sensor and can still provide comparable control performance and training capabilities. While the cost and size of the device can be reduced considerably without a torque/force sensor, patients can use the cost-effective device conveniently and frequently in a local clinic under monitoring of a clinician or at home with initial instruction/training from a clinician. They can also use it in-bed during recovery and rehabilitation.

SUMMARY OF THE INVENTION

In respects of above limitations and problems, the present invention provides a wearable and convertible device and a method for controlling combined motor function training. This device integrates the functions of both passive stretching in said existing CPM devices and additional active assistive training. Without using a force/torque sensor element, the present passive stretching control can still be adapted to hypertonia (high muscle tone or stiffness of joints) of the limb, and the present active assistive control can still be implemented for enhancing voluntary active movement from patients. With present method, much more applications of active assistive training are supported at substantially no additional cost. On the other hand, the safety of such stretching devices without using force/torque sensor is improved, which assists in increasing the efficiency of the device of the present invention.
The present invention can delivery combined self-adaptive passive stretching and assisted/resistance guidance without a torque/force sensor element. Due to the simplified structure, the training device can be worn at an individual joint including ankle, elbow, wrist and knee with neurological impairment or musculoskeletal injuries. The device comprises: 1) a securing portion for securing the training device; 2) a movement portion for securing the limb and is rotatably connected to the securing portion; 3) a motor driving portion secured at the securing portion and is driven by electrical current, wherein the current changes when the limb applies a torque to the movement portion; 4) gearing means for connecting the motor driving portion and the movement portion, wherein the gearing means and the motor driving portion can be moved when the limb applies a torque to the movement portion; 5) a control portion connected to the training device via a control bus, wherein a) the control portion can control the motor driving portion to drive the movement portion to rotate via the gearing means; b) the motor driving portion has a position sensor, which can detect the change of angular position of the movement portion and thus detect the change of angular position of the limb, and the control portion can control the motor driving portion to apply a desired torque to the movement portion based on the detected change of angular position; c) the control portion can detect the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb.
The present invention also provides a control method for performing active assistive and passive stretching training on said training device. Said method comprises the step of performing one or more modes according to the limb training requirement: 1) a mode for compensating inherent resistance force of said motor and gearing, in which the small change of angular position caused by the synchronous movement of the movement portion brought by the active movement of the limb is detected, and the motor driving portion is controlled to apply a torque that is merely enough to overcome the mechanical resistance force of the device so that the limb can move freely; 2) a mode for stretching, in which the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb is detected, the detected change of current is passed through a low pass filter to obtain a smooth value, the rotating speed and range of the movement portion is adjusted according to the change of said filtered current so as to adjust the rotating speed and range of the limb for stretching the muscles of the hypertonic limb; 3) a mode for assisted training and resistance training, in which the change of angular position of the movement portion is detected via the position sensor, the motor is controlled to apply assisting torque or resistance torque that is respective in the same or opposite direction with the movement of the limb, so that assisted training or resistance training can be performed; and 4) a mode for inducing voluntary active movement, in which the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb is detected, and the change of the torque caused by active movement of the limb is estimated according to the change of current, when the change is smaller than a threshold, the motor driving portion is controlled to make the limb do exemplary passive movement, and the movement of the limb is fed back to the patient. Then let the patient move freely, and the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb is detected. According to the change of current, the change of the torque caused by active movement of the limb is estimated, resealed and fed back to the patient. The real time visual and auditory feedback of limb's movement keeps the patient engaged and challenged.
Compared to the existing technologies, the present invention provides a low cost active and passive training device with a simplified structure, and a corresponding control method for impaired limb rehabilitation. Innovations of the system are: (1) further simplify the system structure and components by reducing a force/torque sensor component. The device with simplified structure requires the present control method to detect the joint resistance and voluntary movement intention from a training joint, to accomplish similar functions, which greatly reduces the manufacturing costs. Excluding using electrical current of the motor driving portion as torque estimation, said force/torque sensor refers to a component and a structure used for force/torque measurement, such as stress and strain gauges, torque sensors, spring dynamometer and pressure sensors, etc.; (2) realize controlling the stretching speed and assistance level by detecting the change of angular position and current in the drive portion without an force/torque sensor. And implement the function of safe and self-adaptive passive stretching by using the invented method to overcome the high muscle tone or resistance; (3) invent the structure and control method which can achieve all five following integrated functions, and there is no existing training device which can implement such training combination of all five training modes:
Mode 1. The presented device can output high driving torque in passive stretching, which is enough to fight against hypertonia (high muscle tone or stiffness of joints). According to the detected change of current in the motor driving portion, the stretching speed and the stretching range of motion of movement can be adjusted and adapted to the change of said muscle tone and stiffness.
Mode 2. The presented device can follow user's voluntary active movement. According to the detected change of position in the driving portion, device will generate a torque compensating its inherent resistance, so the user only needs to overcome very small or even no resistance during the training.
Mode 3. This presented device can estimate user's voluntary active movement, and assist limb movement accordingly. The control portion can apply a toque that is in the same direction with the movement direction of the limb to the movement portion so that an assistive force can be applied to the moving limb.
Mode 4. This training device can estimate user's voluntary active movement, and impede the limb movement accordingly. The control portion can apply a toque that is in the opposite direction with the movement direction of the limb to the movement portion so that resistance force can be applied to the moving limb.
Mode 5. This training device can guide and induce user's voluntary active movement. The driving portion generates exemplary passive movement according to the detected changes of position and electrical current, and a rescaled change of the movement can be fed back to motivate user's voluntary active movement.
With the present wearable design, users can wear the wearable device in different training postures, such as lying, sitting, standing and walking, to receive passive/assistive exercise. By attaching different limb braces and splints, the wearable passive/assistive device can fit various individual joint, such as wrist, elbow, knee and ankle joints. Similarly, this method of limb brace replacement can be applied to the present convertible passive/assistive device.
In summary, the present invention can not only free the physical therapist from the strenuous manual stretching, but also provide the effective and accurate stretching training function and induce the patient's voluntary movement. In addition, the present device can implement combined passive stretching and active assistive movement function, which is an essential factor for the motor function recovery on people with neurological disorders and musculoskeletal injuries.
Therefore, the device of the invention is capable of outputting both passive stretching and active assistive movement function so as to meet clinical requirements for motor function recovery on people with neurological disorders and musculoskeletal injuries. The invention proposes a low-cost design structure, so the patients can conveniently use in their own homes and increase their training frequency, so as to shorten their recovery cycle. Compared to previous methods, the invented method can greatly reduce the size, weight and manufacturing costs of the training system and the patient can use the low-cost training devices at home and in local clinics. And for acute patients, they can use the device for the rehabilitation training while in their early stage of recovery.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or further objects, features and advantages of the invention will become more apparent from the following description of exemplary embodiments with reference to the accompanying drawings, in which like numerals are used to represent like elements and wherein:

FIG. 1A is a diagrammatic view of passive/assistive wearable device for elbow joint;

FIG. 1B is a block diagram of execution units in the control portion of the training device;

FIG. 2A is a diagrammatic view of a hand attachment to stabilize passive/assistive wearable device for elbow joint training;

FIG. 2B is a diagrammatic view of a shoulder attachment to stabilize passive/assistive wearable device for elbow joint training;

FIG. 3 is an illustrative embodiment of usage and configuration of passive/assistive wearable device at elbow joint while lying in bed;

FIG. 4 is a diagrammatic view of passive/assistive wearable device for ankle joint;

FIG. 5A is an illustrative embodiment of usage and configuration of passive/assistive wearable device at ankle joint while sitting;

FIG. 5B is an illustrative embodiment of usage and configuration of passive/assistive wearable device at ankle joint while lying in bed;

FIG. 5C is an illustrative embodiment of usage and configuration of passive/assistive wearable device at ankle joint while standing or walking;

FIG. 6 is a diagrammatic view of convertible passive/assistive limb training device;

FIG. 7A is an illustrative embodiment of usage and configuration of convertible passive/assistive limb training device for elbow joint training.

FIG. 7B is an illustrative embodiment of usage and configuration of convertible passive/assistive limb training device for ankle joint training.

FIG. 8A is a flowchart of a control method to compensate mechanical inherent resistance of the passive/assistive wearable device itself;

FIG. 8B is a flowchart of a control method to generate assisted/resistance torque;

FIG. 8C is an flowchart of a control method to adjust stretching strength and stretching range of motion;

FIG. 8D is a flowchart of a control method to induce voluntary active movement;

FIG. 9 is a flowchart of a control method to online switch said control methods (assisted mode, passive mode and resistance mode) based on user training performance;

FIG. 10 is an illustrative embodiment of recording and displaying training performance and the change of joint mechanical properties;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

First embodiment

FIG. 1A shows a diagrammatic view of passive/assistive wearable device for elbow joint.
In one particular embodiment of the device, the wearable elbow device comprises: 1) a securing portion for securing the training device; 2) a movement portion for securing the limb and is rotatably connected to the securing portion; 3) a motor driving portion secured at the securing portion and is driven by electrical current, wherein the current changes when the limb applies a torque to the movement portion; 4) gearing means for connecting the motor driving portion and the movement portion, wherein the gearing means and the motor driving portion can be moved when the limb applies a torque to the movement portion; 5) a control portion connected to the training device via a control bus, wherein a) the control portion can control the motor driving portion to drive the movement portion to rotate via the gearing means; b) the motor driving portion has a position sensor, which can detect the change of angular position of the movement portion and thus detect the change of angular position of the limb, and the control portion can control the motor driving portion to apply a desired torque to the movement portion based on the detected change of angular position; c) the control portion can detect the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb.
As shown in FIG. 1A, the securing portion comprises a securing plate 120 and the first retainer 108. The retainer 108, fixed to the securing plate 120, includes the securing plate 118 and is for securing the impaired limb such as the upper arm to the wearable elbow device. The movement portion comprises the second retainer 109, which includes the securing plate 111. The second retainer 109 is used for securing the impaired limb such as the forearm. The second retainer 109 can rotate with respect to the first retainer 108 along the rotation axis 107; so as to make the impaired limb such as the upper arm supported by the second retainer 109 can rotate with respect to the securing portion along the rotation axis 107. The motor driving portion comprises a motor 101 and a gearbox 102. The motor 101 and gearbox 102 are connected together and supported on the securing plate 120. A section of the second securing plate of the movement portion is connected to the output shaft of the gearbox 102 of the motor driving portion via a coupling, so that the second securing plate can rotate with respect to the first securing plate. The rotation torque is passed from the output of the motor 101 to the output torque of reducer 102 though the gearing means with desired speed and torque. The motor driving portion comprises a position sensor 119, which is connected to the rotating shaft of the motor 101. The position sensor can detect the change of angular position of the output shaft of motor and thus detect the change of angular position of the second retainer 109, thus to detect the change of angular position of the limb movement on the retainer 109 along the rotation axis 107 during the movement. The gearing means comprises a reducer 102, a set of Bevel gears, and a connecting rod 105. The set of Bevel gears comprises a small Bevel gear 103 and a large Bevel gear 104 that engage with each other. The large Bevel gear 104 is connected to the movement portion via the connecting rod 105, the output shaft of the reduce 102 is connected to the small Bevel gear 103 and rotates the large Bevel gear via the small Bevel gear 103. The connecting rod 105 is connected to the second retainer 109 as a whole through the securing plate 111. The control portion 113 is connected to the securing portion through the control bus 112.
In the above structure, when the motor 101 generates a rotation torque, the rotation torque is transmitted to the output of reducer 102 through the gearing means with a desired speed. The output shaft of gearbox 102 is connected to the small Bevel gear 103, which drives the big bevel gear 104 to rotate along the rotation axis 107. Thus the retainer 109 is rotatable while the connecting rod 105 exerting force on it.
As stated above, the present invention of the training device for impaired limb includes a position sensory 119, which can detect the change of angular position of the impaired limb by detecting the change of angular position of the movement portion. Thus the control portion can control the torque applied to the movement portion by the detected position change so that an expected training can be performed on the limb. For example, the control portion can control the motor driving portion to apply a torque that is merely large enough to overcome the mechanical resistance of the training device to the movement portion so that the limb can move freely; and the control portion also can control the motor driving portion to apply a toque that is in the same or opposite direction with the movement direction of the limb to the movement portion so that an assisted training or resistance training can be performed on the limb.
Furthermore, the present invented training device for impaired limb also may comprise a force/torque sensor 106, which is setup between the connection rod 105 and the second retainer 109 in the movement portion. The control portion can adjust the rotation speed and the range of motion according to the signal detected by the force/torque sensor 106 by controlling the electrical current in the motor driving portion, so as to adjust the rotating speed and range of the limb for stretching the muscles of the limb.
However, preferably, the present invention does not include any force/torque sensor. Said additional force/torque sensor refers to the structures used for force/torque measurement excluding using the electrical current of said motor driving portion as torque value estimation, such as stress and strain gauges, torque sensors, spring dynamometer and pressure sensors, etc. As an alternative, the motor control portion detects change of current in the motor driving portion, and then adjusts the rotating speed and range of the movement according to the detected change of current, so as to adjust the rotating speed and range of the limb for stretching the muscles of the limb. The approach significantly simplifies the structure and reduces costs.
In addition, the invented limb training device can further comprise a displayer 114, which displays data and outcome of limb training. And the control portion can further comprise a wireless communication means, which can carry out communication and signal transmitting between the control portion 113 and the displayer 114. And the displayer 114 can further comprises a touch screen, and a patient can manually select different training modes on the touch screen.
As stated above, the present invented limb training device can be in the mode for “assisted training” and “resistance training”. Therefore, the motor 101 and the gearbox 102, the small bevel gear 103 and the big bevel gear 104 need to satisfy certain conditions. First, the total weight of the motor 101 and the gearbox 102 should be smaller than 500 gram, and their sectional diameter should be smaller than 50 mm; Secondly, the movement portion, driven by the gearing means and the motor driving portion, should be able to generate a rotating torque greater than or equal to 15 Nm to satisfy the required stretching of the spasticity/contracture limb. For example, appropriate parameters such as gear ratio should be considered to satisfy the maximum stretching torque; Thirdly, without extra external power from the motor 101, the weak movement applied to the second retainer 109 by the impaired limb should be able to drive the gearing mechanism, including 101, 102, 103, and 104 to rotate synchronously. The change of the angular position should be able to be detected by position sensor 119. So the gear ratio should not be too high and the gearing mechanism should not be a self-locking mechanism. Otherwise, the position sensor has no way to detect the weak movement intention of the limb. Meanwhile, the precision of the position sensor should be greater than or equal to 500 pulses/rotation to ensure the successful detection of the position signal change caused by the weak movement of the retainer 109.
FIGS. 2A and 2B show that when we use the limb training device described in the first embodiment, extra securing straps are needed on the securing portion. The extra securing straps can stably secure the impaired limb (e.g. upper limb) to the training device, and make sure the alignment of the rotation axis 107 and the rotation axis of the elbow flexion/extension movement, so as to avoid the sliding and twisting. Said extra securing straps comprises: a) a shoulder strap 021, with one end connected to the shoulder 002 and b) a chest strap 022 with the other end connected to said limb training device 010. The weight is distributed on the shoulder and chest through the chest straps 022.
As shown in FIG. 2A, the second securing plate of the movement portion of the limb training device 010 comprises a hand grip 013. The patient can hold the hand grip 013, of which the length is adjustable. When the patient is doing certain elbow extension/flexion movement, the hand grip 013 can avoid the relative sliding and twisting between the forearm and the training device. In addition, the extra upper arm securing strap 011 and the forearm securing strap 012 are also used to help secure the limb.
The user 005, as shown in FIG. 3, can use the limb training device 010 while lying on a bed. For example, the acute stroke survival patient can use it during his/her early stage of stroke recovery.

Second Embodiment

FIG. 4 shows the second illustrative embodiment of the invention for ankle joint. The wearable ankle device is similar to the structure of the first illustrative embodiment, and the differences are: the securing component 110 (including 108,118,109 and 111) is replaced by the securing component 140 (including 141,142,144 and 145). In the second embodiment of the invention, the securing part comprises the securing plate 120, the first securing strap 144 and the first retainer 142. The movement portion comprises the securing plate 105, the second retainer 141 and the second securing strap 145. The second retainer 141 can rotate with respect to the first retainer 142 along the rotation axis 143, and the securing component 140 can be replaced by other securing setups, such as knee securing portion or wrist securing portion to achieve different limbs training functions.
As shown in FIG. 5A, FIG. 5B, and FIG. 5C, patients use the same lower limb training device while they are sitting, lying and walking.
The user shown in FIG. 5C, can use the limb training device 150 while lying on a bed. For example, the acute stroke survival patient can use it during his/her early stage of stroke recovery.

Third Embodiment

FIG. 6 shows a third embodiment of the invention installed on the ground for different joints of the limb training device. This device can be installed in different ways to achieve assisted and resistance training for different joints (elbow flexion/extension, wrist flexion/extension, supination/pronation, ankle dorsiflexion/plantarflexion).
Similar to above first and second embodiment, the third embodiment is a training device comprising a securing portion, a movement portion, a motor driving portion, gearing means and a control portion Said securing portion comprises a securing base 616, a first securing plate 614 for securing the motor driving portion, and a height adjusting mechanism 606, the height of the first securing plate 614 can be adjusted via the height adjusting mechanism 606 so as to suit different heights of the joints. Said movement portion comprises a limb securing comprises a limb retainer 607 and a second securing plate 612; said limb retainer 607 is secured on the securing plate 612 and is used for securing the limb. Said motor driving portion comprises a motor 602 and a gearbox 603 connecting to each other, and they are connected to the first securing plate 614 by a securing L-bracket 604. Said motor 602 and said gearbox 603 are secured on the first securing plate of the securing portion via a connection plate 613, a section of said second securing plate 612 of the movement portion is connected to the output shaft of said gearbox of said motor driving portion via a coupling, so that said second securing plat 612 can rotate with respect to the first securing plate 614. The motor driving portion comprises a position sensor 601, which is connected to the rotating shaft of said motor 602. Said position sensor 601 can detect the change of angular position of the output shaft of motor 602 and thus detect the change of angular position of said second securing plate 612, thus to detect the change of angular position of the limb movement on the retainer 607 along the rotation axis 618 during the movement. The gearing means comprises a reducer 603; said reducer 603 is connected to said second securing plate 612 through said connection plate 613. Said control portion 605 is connected to the training device through a control bus.
In above structure, the rotation torque generated by the motor 602 is transmitted to the output of reducer 603 through the gearing means with a desired value in a desired speed. And the rotation torque is then transmitted to said securing plate 612 in the securing portion through said connection plate 613 to make the securing plate 612 and retainer 607 rotate accordingly.
As stated above, the present invention of the training device for impaired limb includes a position sensory 601, which can detect the change of angular position of the impaired limb by detecting the change of angular position of the movement portion. Thus the control portion can control the torque applied to the movement portion by the detected position change so that an expected training protocol can be performed on the limb in a desired speed and direction. For example, the control portion can control the motor driving portion to apply a torque that is merely large enough to overcome the mechanical resistance of the training device to the movement portion so that the limb can move freely; And the control portion also can control the motor driving portion to apply a toque that is in the same or opposite direction of the limb to the movement portion so that an assisted training or resistance training can be performed on the limb.
Furthermore, the present invented training device for impaired limb also may comprise a displayer 611, which displays training protocol, training feedback, and evaluation outcome of limb training. And the control portion can further comprise wireless communication means, which carry out communication and signal transmitting between the control portion and the displayer 611. And the displayer 611 can further comprises a touch screen, and a patient can manually select different training modes and functions on the touch screen.
As stated above, the present invented limb training device can be in the mode for “assisted training” and “resistance training”. Therefore, the motor 602 and the gearbox 603 need to satisfy certain conditions. First, the movement portion, driven by the gearing means and the motor driving portion, can generate a rotating torque greater than or equal to 20 Nm to satisfy the required stretching of the spasticity/contracture limb. For example, appropriate parameters such as gear ratio should be considered to satisfy the maximum stretching torque. Second, without extra external power from the motor 602, the weak movement applied to the second retainer 607 by the impaired limb can be detected and used to drive the gearing mechanism, including 602, 603 to rotate synchronously. That is, the change of the angular position can be detected by position sensor 601 attached to the motor 602. For example, gear ratio should not be too high and the gearing mechanism should not be a self-locking style. Otherwise, the position sensor will be not able to detect the weak movement trend of the limb. Meanwhile, the precision of the position sensor 601 should be greater than or equal to 500 pulses/rotation to ensure the successful detection of the position signal change caused by the weak movement of the retainer 607.
As shown in FIG. 7A and FIG. 7B, the training device can be used for different training functions to train elbow joint, wrist joint, ankle joint, and knee joint by setting up different kinds of limb retainer, such as 702,703 and 607. The patient shown in FIG. 7A use said standing training device 700 and forearm retainer 607 for the elbow training. And the patient shown in FIG. 7B use said standing training device 700 and the foot retainer 703 and leg support 702 for the ankle training.
The control system of said embodiments of invention comprises:
An embedded control unit for executing the invented method, a communication unit for executing the transmission of data and control signals and a portable controlling and displaying platform with touch screen function. The invented control subunit is included in said control unit 180. As shown in FIG. 1B, said control unit 180 comprises: 1) inherent resistance compensating unit 183; 2) assisting/resistance force adjusting unit 184; 3) speed adjusting unit 190. Then control command generated by said control subunit is sent to said motor driving unit through the output execution unit 193.
Said compensating unit 183 comprises a weak signal detecting unit 181 and an inherent resistance compensating unit 182; the weak signal detecting unit 181 detects the small change of angular position of the movement portion caused by the synchronous movement of the movement portion caused by active movement of the limb, then the inherent resistance compensating unit 182 calculates the compensation for overcoming the mechanical resistance of the training device according to the small change of angular position, and controls the motor driving portion 193 to apply the compensating torque to the movement portion so that the limb can move freely;
Said adjusting unit 190 for adjusting assisting force and resistance force comprises a weak signal detecting unit 191 and a assisting/resistance force calculating unit 192. Said weak signal detecting unit 191 reads the change of angular position detected by the position sensor, and the assisting/resistance force calculating unit 192 calculates a desired assisting force or resistance force that is respectively in the same or opposite direction with the movement direction of the limb, and controls the motor to apply the assisting force or resistance force to the movement portion so that the assisted training or resistance training can be performed on the limb;
Said speed adjusting unit 184 comprises an electrical current signal detecting unit 185, an electrical current signal filtering unit 186 and speed adjustment calculating unit 187. Said electrical current signal detecting unit 185 detects the change of current in the motor driving portion caused by a torque applied on the movement portion by the limb, then said electrical current signal filtering unit 186 filters the detected change of current through a low pass filter to obtain a smooth value, then said speed adjustment calculating unit 187 adjusts the rotating speed and range of the movement, so as to adjust the rotating speed and range of the limb for stretching the muscles of the limb.
The system hardware module and the software algorithms are realized in the control portion of the device. Said embedded control unit is connected to the communication unit. The control signals and data are transmitted to said displayer in a wired or wireless way. The functions of said portable controlling and displaying platform include: a) display the human body movement information and training tasks; b) allow patient to set up the training parameters by touching the touch screen and c) connect to the communication unit in order to transmit control parameters.
As stated above, the invented training device should satisfy the follow requirement:
1) The mechanical structure of the motor and gearing means can generate a rotating torque greater than or equal to 15 Nm to satisfy the required stretching of the spasticity/contracture limb. The present invention realizes portable devices with output torque of 15 Nm.
2) The precision of the position sensor in the motor system should be greater than or equal to 500 pulses/rotation to ensure the successful detection of the position signal change caused by the weak movement.
The invented control method has four control modes:
1) Compensating inherent resistance force mode. FIG. 8A shows the flowchart. The main function of the method is to generate a torque that is merely enough to overcome the mechanical resistance force of the device so that the limb can move freely, that is, the mechanical resistance force of the training device will be compensated or negated during the active moment, so the patient only need to overcome very small or even no resistance during the movement.
In this mode, the detecting unit 181 shown in FIG. 1B detects the position change per unit time □P when the limb rotates and thus drives the movement portion synchronously; Then the compensating unit 182 generate a controlling current I_bkin the same direction of limb movement. The controlling current I_bkdrives the motor and the limb move in the same direction. As a resistance compensation algorithm example, the formula (1)
$\begin{matrix} I_{bk} = {\begin{matrix} I_{friction_A} + G_{_A} * Δ P, & if Δ P >= P_{0} \\ G_{start} * \sin (t), & if \langle Δ P \rangle < P_{0} \\ I_{friction_B} + G_{_B} * Δ P, & if Δ P = < - P_{0} \end{matrix} & (1) \end{matrix}$
in which I_friction _— _Astands for a component of the driving current for compensating the mechanical inherent resistance when the limb is moving along the defined positive direction, I_friction _— _Bstands for a component of the driving current for compensating the mechanical inherent resistance when the limb is moving along the defined negative direction, G_A,G_Brepresent the proportional gain coefficient of the position change per unite time ΔP, G_startis a predetermined amplitude, P₀is a predetermined threshold.
When the position change per unit time ΔP is greater than the predetermined threshold P₀, the controlling current I_bkwill determined by I_friction _— _Aand G_A·ΔP according to formula (1) and sign “*” in formula (1) stands for a multiply operation; when the position change per unit time ΔP is smaller than or equal to −P₀, the controlling current I_bkwill determined by I_friction _— _Band G_B·ΔP according to formula (1); When the absolute value of the position change per unit time ΔP is smaller than P₀, the controlling current I_bkwill determined by G_start·sin(t) according to formula (1).
Then according to controlling current I_bk, said motor driving portion will generate corresponding torque, that is merely enough to overcome the mechanical resistance force of the device so that the limb can move freely, that is, the mechanical resistance force of the training device will be compensated or negated during the active moment, so the patient only need to overcome very small or even no resistance during the movement.
2) Stretching mode. This mode is used for adjusting the movement speed and stretching range when the output torque of the training device is relatively high (high torque is used for stretching the limb), so as not to cause the induced pathological limb spasticity and high muscle tension.
FIG. 8C shows the flowchart for this mode. As shown, the current I_stretchingof the motor required to maintain the prevailing stretching speed is calculated by the adjusting unit 184; as the stretching amplitude increases during the movement, the motor driving portion continuously increases I_stretchingso as to generate a higher stretching torque to overcome the higher and higher muscle tension or resistance; the change of the muscle tension is estimated by detecting the current I_stretching: when the current I_stretchingincreases, the stretching speed V_adjustis changed by the calculating unit 187 according to the change of I_stretching, the formula (3)
$\begin{matrix} V_{adjust} = V_{\max} * (1 - \frac{Filtered (I_{stretching})}{I_{\max_stretching}}) & (3) \end{matrix}$
in which I_max _— _stretchingrepresents the maximum current allowed in the motor, namely, the allowed maximum output torqued, V_maxrepresents the allowed maximum stretching speed, and Filtered (I_stretching) stands for the smooth value of the detected change of current obtained through low-pass filtering. The stretching speed V_adjustis decided by the controlling current I_stretchingaccording to formula (3) and the symbol “*” in formula (3) stands for a multiplication operation. During the stretching, when the needed I_stretchingfor stretching increases, the stretching speed V_adjustwill decrease according to formula (3). And when the needed I_stretchingfor stretching increases to the threshold I_max _— _stretching, the device will not further increase the stretching torque, thus the stretching speed V_adjustwill decrease to 0 according to formula (3). The threshold I_max _— _stretchingis decided by the maximum stretching torque the limb can bear. During the whole stretching process, as the muscle tension increases, the training device provides a training strategy to adjusting the stretching speed accordingly.
3) Assisted/Resistance training mode. FIG. 8D shows the flowchart for this mode. In this mode, the limb training device generates assisting force or resistance force to assist or impede the movement of the impaired limb. That is, the patient will feel the assisted force in the same direction with the movement or the resistance force in the opposite direction with the movement.
In this mode, the position change per unit time ΔP is detected by the detecting unit 191 when a weak active movement generated by the limb rotates the movement portion synchronously; and then the calculating module 192 will generate a controlling current I_bkthat is in the same or opposite direction with the movement direction according to the detected position change ΔP and the predetermined training target, so as to control the motor to generate assisting force or resistance force. As an example of the assisting/resistance force generation algorithm, the value of the assisting/resistance force can be determined by formula (2)
$\begin{matrix} I_{bk} = {\begin{matrix} I_{friction_A} - (I_{constant_A} + R_{_A} * Δ P), & if Δ P > 0 \\ 0, & if Δ P = 0 \\ I_{friction_B} - (I_{constant_B} + R_{_B} * Δ P), & if Δ P < 0 \end{matrix} & (2) \end{matrix}$
in which I_constant _— _Astands for a constant value of the driving current for generating the corresponding constant resistance force when the limb is moving along a defined positive direction, I_constant _— _Bstands for a constant value of the driving current for generating the corresponding constant resistance force when the limb is moving along a defined opposite direction, R_A,R_Brepresent the proportional gain coefficient of the position change per unite time ΔP. The controlling current I_bkwill be determined by formula (2) and sign “*” in formula (2) stands for a multiply operation.
When the position change per unit time ΔP is equal to the predetermined threshold 0, The controlling current I_bkwill be equal to 0, which means the motor output torque is 0 according to formula (2). When the position change per unit time ΔP is greater than the predetermined threshold 0, The controlling current I_bkwill be determined by I_friction _— _A, I_constant _— _A, and R_A*ΔP according to formula (2). When the position change per unit time ΔP is smaller than or equal to the predetermined threshold 0, The controlling current I_bkwill be determined by I_friction _— _B, I_constant _— _B, and R_B*ΔP according to formula (2).
Then said motor driving portion will generate corresponding torque by controlling the driving current I_bk. The sign of R_A, R_Bdetermine which kind of torque should be generated (assisting force or resistance force). And the amplitude of R_A, R_Bdetermines the change velocity of the force/torque.
4) Inducing active movement mode. The main function of the method is to induce patient's active moment when the impaired limb has no function of active moment.
In this mode, the change of current in the motor driving portion caused by a torque applied to the movement portion by the limb is detected, and the change of the torque caused by active movement of the limb is estimated according to the change of current, when the change of the torque is smaller than a predetermined value, the motor driving portion is controlled to make the limb do exemplary passive movement, and the movement of the limb is fed back to the patient visually and auditorily. After the stretching demonstration, the patient is required to move the limb by themselves. Then the weak change of current in the motor driving portion caused by a torque applied to the movement portion by the limb is detected, and the change of the torque caused by active movement of the limb is estimated according to the change of current, and change of the torque is resealed and fed back to the patient visually and auditorily. The change of the torque being displayed could be bigger than the real one to guide the patient conducting the active movement training and could also be smaller than the real one to encourage the patient to increase their strength and range of stretching.
Combining the above 4 training modes in the training process will assist patient to perform the movement task.
As shown in FIG. 9, the program of said 4 control modes will be stored in said embedded control unit, which will automatically choose different training mode according to the change of the electrical current and position of the driving motor when the limb is moving. During the training, said training task and movement target could be displayed to patient through visual or audio games. As a control example, the patient is required to move their limb to the predetermined position. Otherwise, the training device will be running in said first mode to allow the patient move freely without resistance. Then, said control system detects the change of position of said movement portion and the limb, and compares them with the target position. If said change of the position is bigger than the preset change of position, and the change vectors are in the same direction, then the device will be still running in the free mode; If said change of the position is smaller than the preset change of position, then the device will be still running in the assisted mode, providing assisting force to help patient move to the target position. During the process, if said motor driving current reaches the maximum driving current, the limb training device will be running in the passive stretching mode, make sure no stronger assisting force will be applied to the limb which may cause the limb injury.
The method of recording and displaying the human body movement information is stated as follows.
According to the basic principle of the motor torque generation, due to its mechanical structure, brushless motor is more efficient than the brush motor with the same size and weight. The output torque is in proportion to the driving current. So we choose brushless motor to power said training device, and use the change of the electrical current as an estimation of the change of the resistance (contracture and high muscle tension). We can draw a graph showing the relationship between a specified current and the corresponding output. As shown in FIG. 10, 80% current corresponds to a real output torque of 20 Nm (100% current equals to 5 A). During the training said training device can record the driving current used for overcoming the joint resistance in different rotation positions. The application program can draw the “current change vs. limb rotation” curve, the passive range of motion and the active movement strength.
In sum, an active and passive limb training device and a control method are introduced through illustrative embodiments of the invention. While some embodiments of the invention have been described above, for the illustrative purpose only, it is to be understood that the invention is not limited to the details of the illustrated embodiments, but may be embodied with various changes, modifications or improvements, which may occur to those skilled in the art without departing from the spirit and scope of the invention.

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Claims

1-5. (canceled)

6. The training device according to claim 1, wherein the control portion, without using a force sensor or a torque sensor components, includes one or more of the following means:

7. The training device according to claim 6, wherein the movement portion, driven by the gearing means and the motor driving portion, can generate a rotating torque greater than or equal to 15 Nm.

8. The training device according to claim 6, wherein the precision of the position sensor is greater than or equal to 500 pulses/rotation.

9. The training device according to claim 6, wherein the training device is wearable, the securing portion comprises a securing plate and a first retainer, the first retainer is secured to the securing plate and is used for securing the training device to a human body part.

10-15. (canceled)

16. The training device according to claim 6, wherein the training device is a standing device, the securing portion comprises a securing base, a first securing plate for securing the motor driving portion, and a height adjusting mechanism, the height of the first securing plate can be adjusted via the height adjusting mechanism so as to suit different heights of the joints.

17-18. (canceled)

19. The training device according to claim 6, wherein the training device further comprises a displayer, which displays data and outcome of limb training.

20-25. (canceled)

26. The method according to claim 25, wherein

in which I_friction _— _Astands for a

I_{bk} = {\begin{matrix} I_{friction_A} + G_{_A} * Δ P, & if Δ P >= P_{0} \\ G_{start} * \sin (t), & if \langle Δ P \rangle < P_{0} \\ I_{friction_B} + G_{_B} * Δ P, & if Δ P = < - P_{0} \end{matrix}

component of the driving current for compensating the mechanical inherent resistance when

I_{bk} = {\begin{matrix} I_{friction_A} + G_{_A} * Δ P, & if Δ P >= P_{0} \\ G_{start} * \sin (t), & if \langle Δ P \rangle < P_{0} \\ I_{friction_B} + G_{_B} * Δ P, & if Δ P = < P_{0} \end{matrix}

the limb is moving along the defined positive direction, I_friction _— _Bstands for a component of the driving current for compensating the mechanical inherent resistance when the limb is moving along the defined negative direction, G_A,G_Brepresent the proportional gain coefficient of the position change per unite time ΔP, G_startis a predetermined amplitude, P₀is a predetermined threshold.

27. (canceled)

28. The method according to claim 27, wherein

V_{adjust} = V_{\max} * (1 - \frac{Filtered (I_{stretching})}{I_{\max_stretching}})

V_{adjust} = V_{\max} (1 - \frac{Filtered (I_{stretching})}{I_{\max_stretching}})

I_max _— _stretchingrepresents the maximum current allowed in the motor, namely, the allowed maximum output torqued, V_maxrepresents the allowed maximum stretching speed, and Filtered (I_stretching) stands for the smooth value of the detected change of current obtained through low-pass filtering.

29-30. (canceled)