GB2154339A

GB2154339A - A control system for an instrument carried by a robot arm

Info

Publication number: GB2154339A
Application number: GB08403786A
Authority: GB
Inventors: Alan David Wiley; Derek James Pasquire
Original assignee: BL Technology Ltd
Current assignee: BL Technology Ltd
Priority date: 1984-02-14
Filing date: 1984-02-14
Publication date: 1985-09-04
Also published as: GB8403786D0

Abstract

A control system for a paint spray gun (Figs. 1,2 not shown) carried by a robot arm. Movement of the robot arm is controlled by a main microprocessor unit (7), and process variables of the gun such as paint flow rate, paint spray fan width and atomisation air pressure are controlled by an operational microprocessor unit (8) in synchronism with the movement of the robot arm. "On-line" adjustments of the process variables can be made by means of joy-stick controls (9) connected to the operational microprocessor unit (8) without affecting the main microprocessor unit (7). <IMAGE>

Description

SPECIFICATION A control system for an instrument carried by a robot arm This invention relates to a control system for an instrument carried by a robot arm.

Robot control systems are, for instance, used in a vehicle paint spray line to control robot arms carrying paint spray guns . The programming of such robot arms and of the paint spray guns carried thereby is an extremely skilled task as movement of the gun has to be critically controlled to achieve a consistent paint finish for a given set of process conditions.

Reprogramming of the robot arm and paint spray gun is required as process conditions vary and this is time consuming and laborious.

According to this invention there is provided a control system for an instrument carried by a robot arm comprising: operational control means for controlling process variables of the instrument, the operational control means being arranged to be connected to and function in syncronism with main control means which control movement of the robot arm; and adjustment means for adjusting the operational control means independantly of the main control means to effect changes in the manner the process variables are controlled.

Preferred features of this invention will become apparent from the subsidiary claims of the specification.

This invention will now be described, merely by way of example. with reference to the accompanying drawings, in which: Figure 1 is a plan view of a paint spray gun which may be controlled by a system according to the present invention; Figure 2 is a side view of the paint spray gun of Figure 1; and Figure 3 is a box diagram illustrating a system according to the present invention connected to a robot arm control unit and connected to control a paint spray gun such as that shown in Figures 1 and 2.

Figures 1 and 2 illustrate a paint spray gun 1. Such a gun may have a number of controls for altering variables affecting the paint spray produced by the gun and the iliustrated gun is provided with a paint flow control 2 which controls the rate of paint flow to the gun and hence the amount of paint leaving a nozzle 3 of the gun, a fan width control 4 which controls the width of the paint spray fan emitted from the nozzle 3, and an atomising air pressure controls which controls the pressure of air supplied to the gun to atomise paint emitted from the nozzle 3. The gun 1 has an intrinsically safe actuation system comprising either hydraulic, fully encapsulated motors 6 (see Figure 3) or pneumatic actuators (not shown) for operating the controls 2, 4 and 5 thereof.

The gun 1 is arranged to be carried by a robot arm (not shown) so that it is moved around a predetermined path to effect painting of an article such as a vehicle body (not shown). Movement of the robot arm is controlled by a main control or robot arm control unit 7 shown in Figure 3. The robot arm control unit 7 is a microprocessor which controls the positioning of the gun 1, the orientation of the gun 1, and the speed of movement of the gun 1. Thus, under the control of the robot arm control unit 7, the gun 1 is moved around a predetermined path over the surface of a vehicle body to effect the desired painting of the body. The speed of movement of the gun 1 is synchronised with movement of the vehicle body along a production line. Such a robot arm control unit is known in the art and will not therefore be described further.

As the gun 1 is moved around the predetermined path over a vehicle body, process variables such as the paint flow rate, paint spray fan width and atomising air pressure have to be controlled. These variables may be set to predetermined levels or may be controlled in a predetermined manner in synchronism with the movement of the robot arm. However, control of the process variables needs to be altered as process conditions such as paint viscosity, temperature, and line speed vary.

The reduction in paint viscosity on a hot day may, for instance, cause drips on the vehicle body being painted. As shown in Figure 3, an operation control unit 8 is thus provided to control the actuation system 6 of the paint spray gun 1 and thus control process variables such as the paint flow rate, the paint spray fan width. and the atomising air pressure. The operational control unit 8 comrises a microprocessor which is connected to the main control unit 7 by a data line and a clock signal line and it operates in synchronism with the robot arm control unit 7. An adjustment joy-stick control unit 9 is connected to the microprocessor 8 to effect changes in the manner in which the microporccesor 8 controls the process variables. The joy-stick control unit 9 may, for instance, comprise a plurality of centrally biased, spring loaded joysticks.The microprocessor 8 is provided with two memories, a first memory 8A which retains a program for controlling the process variables in a predetermined manner, and a second memory 8B which acts as a scratch pad to store a program for controlling the process variables as determined by adjustments made to the joy-stick control unit 9.

When "on-line" adjustments of the program stored in the second memory 8B are completed, the amended program can be transferred to the first memory 8A. Thus, a predetermined program is securely retained by the first memory 8A whilst the program in the second memory 8B is being edited. When the editing is complete, the program stored in the first memory 8A is up-dated by that stored in the second memory 8B. It would also be possible to provide a further memory which retains the predetermined program indefinitely to ensure that a standard, or basic, program is always available.

In operation, the robot arm control unit 7 is first programmed to produce all necessary movements of the robot arm and hence of the paint spray gun 1 carried thereby. This program incorporates a standard predetermined program for controlling the process variables of the gun 1. This first step can, of course, be omitted if a robot arm control unit is already installed and appropriately programmed.

Next, with the operational control unit 8 connected to the main control unit 7, the program is replayed and control of the process variables simultaneously edited by means of the joy-stick control unit 9. If the joy-sticks are left in their central positions, the process variables are controlled in accordance with the predetermined program. However, if the operator moves any of the joy-sticks he can make "on-line" adjustments to the program controlling the process variables. The amended program is initially stored in the second memory 8B of the microprocessor 8. When the program has been amended to the satisfaction of the operator, the predetermined program stored in the first memory 8A can be up-dated by the amended program stored in the memory 8B.

A plurality of paint spray guns may, of course, be controlled by one central operational control unit 8.

Each robot arm is preferably controlled by a respective robot arm control unit 7 but a plurality of robot arms may be controlled by one central operational control unit 7.

The separation of the robot arm control unit and the operational control unit thus permits adjustments to be made to the process variables of the paint spray gun to account for changes in process conditions without the need for time consuming and laborious reprogramming of the robot arm control unit itself.

The adjustments can, therefore, be made "online" as changes in the process conditions occur whereby "fine-tuning" of the process variables can easily be effected without affecting the robot arm control program. In addition, the robot arm control unit need only be made accessible to programming personnel whilst the operational control unit can be made accessible to personnel operating the paint spray line.

It will be appreciated that this invention is applicable to other robot controlled processes in which an instrument is carried by a robot arm, and that the invention can be incorporated into an existing robot controlled process to provide independant control of process variable of instruments carried by robot arms.

Claims

1 A control system for an instrument carried by a robot arm comprising: operational control means for controlling process variables of the instrument, the operational control means being arranged to be connected to and function in syncronism with main control means which control movement of the robot arm; and adjustment means for adjusting the operational control means independantly of the main control means to effect changes in the manner the process variables are controlled.

2 A system as claimed in claim 1 in which the operational control means comprises a microprocessor having a first memory for storing data to control the process variables in a predetermined manner, a second memory for storing data to control the process variables in a manner determined by operation of the adjustment means, and transfer means for transferring data from the second memory to the first memory when "on-line" operation of the adjustment means has been completed.

3 A system as claimed in claim 2 in which the adjustment means comprises at least one centrally biased joy-stick control operation of which changes the data stored in the second memory.

4 A system as claimed any preceding claim in which the operational control means is arranged to control operation of a paint spray gun.

5 A system as claimed in claim 4 in which the operational control means is arranged to control process variables such as the rate of paint flow to the gun, the fan width of a paint spray produced by the gun and the pressure of an atomising air supply fed to the gun.

6 A system as claimed in claim 4 or 5 in which the gun is carried by a robot arm and the operational control means is connected to main control means arranged to control movement of the robot arm and hence the gun around a predetermined path over an article to be painted.

7 A system as claimed in claim 6 in which the main control means is arranged to control variables such as the position of the gun, the orientation of the gun and the speed of movement of the gun.

8 A control system for an instrument carried by a robot arm substantially as herein described with reference to the accompanying drawings.

9 A paint spray line equipped with at least one system as claimed in claim 6, 7 or 8.