WO1994001812A1

WO1994001812A1 - Method for controlling machining units

Info

Publication number: WO1994001812A1
Application number: PCT/SE1993/000617
Authority: WO
Inventors: Carel Jibben; Kurt Jonsson
Original assignee: Contractor Tools Ab
Priority date: 1992-07-13
Filing date: 1993-07-09
Publication date: 1994-01-20
Also published as: AU4594193A; SE9202160L; SE9202160D0

Abstract

The invention relates to a method for steering the working units (2) of working machines (1) in a horizontal plane (x, Y) and in an inclined plane. The invention is characterized by storing in a control computer (4) carried by the machine (1) values which determine the position, slope and configuration in space of the target surface (12) to be produced; feeding the control computer (4), via radio link (8), with information from at least one homing total station (3) whose spatial coordinates are known to the control computer (4) relating to the position of a reflector (5) carried by the working machine (1) in relation to the homing total station (3) as the machine (1) works, wherein the position of the reflector (5) in relation to the working unit (2) is determined; and controlling the working position of the working unit (2) in space with the aid of the control computer (4) on the basis of the values stored in the control computer and on the basis of the information supplied by the homing total station (3).

Description

Method for Controlling Machining Units

The present invention relates to a method according to the preamble of Claim 1, for automatically controlling earth or soil working machines so as to facilitate levelling of the ground and increase the efficiency and precision of the machine concerned. Automatic control systems which include a rotary laser beam as a reference plane or datum level for earth or soil working machines which require a reference plane in the form of a flat surface are known to the art. This plane or surface may slope around one or two axes, but may in no way be curved. Reference is made by way of example to Swedish Patent Specification 334,76 and to U.S. Patent Specification 4,677,555 in this regard.

Thus, control systems for machining units of working machines, such as road planers, bulldozers, graders, asphalting machines and like machines are commercially available, said systems enabling the operative or working units to be steered automatically to conform to any geometric shape of the surface to be produced by the machine. This surface - the target surface - may be the surface of a road, an aircraft runway, a foundation site, a plot of ground, etc., to be ma¬ chined.

The surface that is to be machined - the target sur¬ face - is normally not flat, but has a three-dimen- sional shape in space. The inventive method does not restrict the control system to work carried out in solely one plane, i.e. two-dimensional work, but enables the machine to be guided in any desired direc¬ tion and the operative units to be guided in vertical directions without the operator-driver needing to change settings. The operator may have only a guiding or steering function in the horizontal plane, although this function may, of course, be managed by the con¬ trol system. This is possible owing to the fact that the invention is characterized by the characteristic features set forth in the following Claim.

The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawing, in which Fig. 1 is an overview of the method according to the invention, with the working machine shown from above and from one side for the sake of illustration; Fig. 2 illustrates a surface to be produced; Fig. 3 is a schematic illustration of the machine at work; and Fig. 4 is a view of the machine at work, although on a larger scale.

Briefly, the components concerned include a working machine 1, which in the illustrated embodiment is a road planer which carries and drives operative units 2, in the illustrated case a road planing blade. The machine 1 is equipped with a control computer 4 and a reflector 5, whose position in relation to the working unit 2 is known by the control computer 4. The refer¬ ence numeral 6 identifies the operator or driver of the machine, while the reference numeral 7 indicates reference points placed on the target surface.

It will be understood that the working units, in this case the road planing blade 2, is anchored in the machine by means of power sources - either electrical or hydraulic power sources - which move and set the blade so that it will conform to the requirements of the target surface. The target surface can be des¬ cribed in the terms of a three-dimensional model which is stored in a personal computer, either by manually keying-in the values or via a connected CAD system. The machine 1 is also equipped with a control box/- mobile industry computer, and the working units that are to work the area concerned to achieve conformity with the target surface are provided with means which continuously feed to the control box values relating to position (absolute coordinates in three axes), slope (inclination) and direction.

The control box is provided with the following func- tions:

Storage of machine parameters (relative measure¬ ments) . Loading of the relevant values from the 3D model. - Initiating positional calculations.

Storage of parameters that describe the nature of the initial surface, from very irregular to very smooth. Input of desired height differences in relation to the target surface.

Continued positional calculations of the working units in comparison with the target surface. Control signals to the working units. Graphic position indication to the operator.

The three-dimensional model thus describes the surface to be worked and implemented in the PC-program. The values of the surface to be worked can be inserted in different ways:

By manual keying of the values (road axis coordi¬ nates - x, y, z , straight sections, transition curves, curves, the width of road halves, grad¬ ing). - By connecting-up to a CAD system which manages the planning of the target area concerned.

The input values are stored in a database in a coded form. Some of the values stored in the database are transferred to the control box 4 in the machine 1.

This is a one-time procedure effected with the aid of a data cable, modem or like means. The homing or target-seeking total station 3 has the function of an automatic geodimeter which is anchored on a fixed point adjacent the area to be worked. The homing total station 2 continuously tracks the re¬ flector 5 mounted on the machine 1. As before men¬ tioned, the position of the reflector 5 is fixed in relation to the operative units 2 and is known to the control computer 4, which also knows the position of the operative units.

The total station 3 measures the position of the reflector 5 in space (in the terrain) at regular intervals as the machine works. The position is given by the three values - horizontal angle, height angle and distance. These values are sent to the control box 4 in the machine 1, via a radio link 8. The position x, y, z of the operative unit is ascertained in the control box. It will be understood that the position of the operative unit 2 must be calculated immediately and continuously. Furthermore, this positional calcu¬ lation must be absolute, which in turn requires the calculations to commence from a fixed point, namely said total station 3. The position of the reflector 5, and thus also the position of the operative unit 2, is calculated continuously on the basis of this fixed point.

The direction of movement of the machine is calculated by interpolating the present or instantaneous x, y position with preceding positions with the aid of a simple indicator which indicates driving in a forward or backward direction. It can be mentioned in this regard that satellite positioning techniques will probably be developed so as to enable the work of the total station (the geodimeter) to be handled by a GPS, Global Positioning System, and consequently reference to a total station in this document shall also be considered to include a global positioning system within the scope of the present invention. The values relating to the target surface 12 are fed into the control computer 4, as are also the positions of the reference points 7. The homing total station 3 is levelled vertically, but can be given any desired horizontal orientation. The homing total station 3 fixes a bearing on one of the reference points 7 and sends to the control computer 4 in the machine 1, via said radio link 8, the values of horizontal angles, vertical angles and distance of the homing total station 3. The homing total station 3 then fixes a bearing on the next reference point 7 and sends infor¬ mation to the control computer 4 corresponding to the preceding reference point. The operator 6 feeds those reference points 7 that have been fixed into the control computer 4.

The control computer mounted in the machine 1 has the following functions:

- Storage of machine parameters, such as the posi¬ tion of the reflector 5 in relation to the opera¬ tive units 2, the working field of the operative units, and the movement plan of the machine; loading of the measurement values from the target surface 12 in the control computer, these values needing to be loaded only once with each project; initiating positional calculations, i.e. each time the homing total station 3 is moved and placed on another fixed point, it is necessary that the control system - the control computer

4 - is aware of the position and orientation of the homing total station. This is effected by sighting the total station 3 onto a reflector which is located on two or three known measuring points - reference points 7. When the total sta¬ tion 3 fixes a bearing on these points, the con¬ trol system in said machine - the control comput¬ er 4 - shall be informed of the measuring point or measuring points whose bearing/bearings has/have been fixed at that moment, so that the control computer is able to calculate the new position and orientation of the total station 3; also storing in the control computer parameters which describe the nature of the initial starting surface. This parameter is put into use when the operative units 2 shall be steered; input of desired height difference in relation to the target service 12; - continued calculation of position and orientation of the operative unit; target slope, slope of the operative unit, target height of the unit in comparison with the true height of the working unit 2, control of the height changes of the working unit; and includes a graphic terminal on which the position and orientation of the machine can be shown to facil¬ itate handling of the machine 1 by the operator 6.

The control computer 4 has thus established the x, y, z coordinates of the homing station 3 and also the orientation of the station. As the machine 1 works, the homing total station 3 fixes a bearing on the reflector 5 and is instructed to track the reflector 5 as it moves within the target area 12 - Figs. 2 and 3. The control computer 4 is constantly aware of the x, y, z position of the reflector 5 in the target area, via the homing total station 3, and calculates contin- uously and compares continuously the true height of the reflector 5 with the theoretical height of the x and y coordinates of the reflector, because it may be necessary for the working unit 2 to adopt a position which lies at a specific distance above or beneath the target surface during the actual construction work.

The control computer 4 thus controls the working unit 2 vertically, so as to take a given distance above (10-positive) or beneath (11-negative) the target surface 12. The control computer 4 also calculates continuously the slope or inclination 13 of the work¬ ing unit 2, determined by target surface input data.

It will be understood that the machine includes a forward/rearward indicator means and a horizontal angle indicator means. Forward/rearward indications are effected with the aid of a signal coupled to the gearbox of the vehicle. The horizontal angle indicator gives the angle between the working unit 2 and the machine 1. This can form part of an existing system in the machine 1, when the machine is intended for laser control.

The working range of the machine can be increased by using several homing total stations simultaneously, each having its own radio link 8 and being positioned at appropriate sites. The position of each such total station shall, of course, be known to the control computer 4. The precision of the system can also be enhanced by using several homing total stations simul¬ taneously.

Claims

Claim

1. A method for controlling the working units (2) of working machines (1) in a horizontal plane (x, Y) , in a vertical plane (Z) and in an inclined plane, c h a r a c t e r i z e d by storing in a control computer (4) carried by the machine (1) values which determine the position, slope and configuration in space of the target surface (12) to be produced; feeding the control computer (4), via radio link (8), with information from at least one homing or target- seeking total station (3) , whose spatial coordinates are known to the control computer (4), relating to the position of a reflector (5) carried by the working machine (1) in relation to the homing total station (3) as the machine (1) works, the position of the reflector (5) in relation to the working unit (2) being determined; controlling the working position of the working unit (2) in space with the aid of the control computer (4) on the basis of the values stored in the control computer and on the basis of the infor¬ mation supplied by the homing total station (3) .