JPS6344204A - Digital control device for robot - Google Patents

Abstract

PURPOSE:To improve control performance, by varying a sampling time corresponding to the number of moving axes, at the time of calculating the optimum operating quantity at every sampling time based on a mathematical model. CONSTITUTION:The control device of a robot (articulated robot) 1 having a number of degree of freedom is constituted of a digital control device 2 provided with the mathematical model 3 of an arm, the managing part 5 of a control means, and the calculation part 6 of the optimum operating quantity. At this time, a means 7 which sets the sampling time corresponding to the moving axis, and also, the mathematical model 8 corresponding to the sampling time, are generated in the model 3, and are stored in a storage device in advance. In this way, the number of the moving axes are decided after the completion of an operation until the current time is confirmed by a sensor signal, at the time of performing control actually, and the sampling time corresponding to a bearing is selected. And the mathematical model 8 corresponding to a selected time is selected, and the robot 1 is controlled by the time.

Description

[Detailed Description of the Invention] [Summary] In order to obtain higher control performance in the digital control of a robot that has many degrees of freedom, the present invention makes the sampling time variable and determines the appropriate sampling time according to the number of moving axes. This allows you to choose.

[Industrial application field]

The present invention relates to a digital control device for a robot.

[Conventional technology]

With the development of microelectronics, digital control has come to be used in robots as well. Unlike continuous-time control, digital control is essentially discrete-time control, so it is necessary to shorten the sampling time as much as possible in order to improve the control performance of the robot.

FIG. 3 shows a conventionally commonly used digital control system. In the figure, 1 is an articulated robot, 2 is a digital control device (usually a computer), 3 is a mathematical model storage for the articulated robot, 4 is a power amplifier, 5 is a control strategy management unit, and 6 is an optimal operation. This is the quantity calculation part.

Upon receiving a sensor signal 2 from the robot 1, for example, an encoder signal θ indicating the rotation angle of a motor, the digital controller 3 converts the control object it has internally, in this case a mathematical model of the arm of the robot 1 ( For example, based on the equation of state model or transfer function model) 3, the optimum operation amount calculation unit 6 calculates the optimum operation amount for controlling arm positioning or trajectory control, etc. It is sent to the robot via

Under such control, the mathematical model 3 of the robot arm expressed in a continuous time system is discretized by the sampling time determined by the computing power of the computer, etc., and the robot 1 is controlled by this discretized model. be exposed.

That is, it is assumed that the state equation model 3 of the arm is given in the following continuous time system.

y=Cx Here, X is a state variable and U is a manipulated variable.

Letting the sampling time be T and converting this to a discrete time system, x (k+1)=Fx (k) 1 Gu (k))'
(k) =C-x (k)F= I +AT
+ (AT)” /2 !+ (AT)’ /3 !+
... becomes. Here, A, B, C, F, and G are matrices of appropriate dimensions, and ■ is a unit matrix.

[Problem that the invention seeks to solve]

In conventional digital control devices, once the sampling time is determined as described above, a mathematical model of the robot arm is determined based on this, and this model is used to perform control from beginning to end.

In this way, control is performed using a fixed model with a fixed sampling time, so even if many axes move in an articulated robot, or only some axes move, the sampling time is the same, so there is no waste. This is disadvantageous in terms of improving control functions.

An object of the present invention is to improve control functions by making it possible to select an appropriate sampling time depending on the number of moving axes.

[Means for solving problems]

The present invention will be explained in detail with reference to the principle block diagram of the robot control device of the present invention shown in FIG.

1 is a robot with many degrees of freedom (in this case, an articulated robot), 2 is a digital control device, 3 is a mathematical model of the arm stored in the storage device within the device, 4 is a power amplifier, and 5 is a control The policy management unit 6 is an optimal operation amount calculation unit.

In the present invention, a sampling time corresponding to the number of moving axes is set (7 in the same figure), a mathematical model (8 in the same figure) is created according to each sampling time, and each of them is stored in advance in the storage device. Store it in

When actually controlling the robot, after confirming that the operation up to the present point has been completed using sensor signals, the number of moving axes is determined, the sampling time is selected according to this number of axes, and the selected sampling time is A corresponding mathematical model was selected, and the robot was configured to be controlled according to this mathematical model.

[For production]

Based on a sensor signal from the robot 1, such as an encoder signal θ indicating the rotation angle of the motor, the control device 2 knows that the control up to this point has been completed, and sets the next target. At that time, the movement (number of axes) of the robot arm is determined.

When the number of moving axes is small, the amount of servo calculations is small, so the sampling time is short. Therefore, a short sampling time is selected, and an arm model corresponding to this is used for control.

When there are many moving axes, the amount of calculation for the servo is large, so a long sampling time commensurate with the amount of calculation is selected, and an arm model corresponding to this is selected and used for control.

The optimum operation amount determined based on each selected model is then given to the robot through the power amplifier 4.

In this way, in the present invention, control is performed with a sampling time that corresponds to the number of moving axes, so control is executed in the shortest possible time, and deterioration in control performance is prevented.

〔Example〕

An embodiment of an articulated robot with six degrees of freedom constructed using the present invention will be described below with reference to the drawings.

FIG. 2 is a flowchart showing the procedure of positioning control in the above embodiment.

When it is detected from the sensor signal 9 from the robot (see 1 in FIG. 1 above), for example, the encoder signal θ indicating the rotation angle of the motor as described above, that the control up to this point has been completed, the control strategy management unit 5 [ Refer to FIG. 1] performs the following processing.

First, determine the next target value, decide whether to perform trajectory control or positioning control to reach this target value (10 in Figure 2), and also determine which axis needs to be moved. Determine [11 to 16 in Figure 2].

Next, in mathematical model 3, the sampling time corresponding to the number of moving axes determined above is read out [2 in Figure 2].
1 to 26], and a mathematical model corresponding to this sampling time and the moving axis is selected [31 in FIG. 2].

When the arm model is selected from the mathematical model 3, the read sampling time is set in the optimum operation amount calculation section 6, and a sampling time timer is started (41 in FIG. 2). Next, the optimum operation amount (servo) is calculated [42 in FIG. 2], and the calculated optimum operation amount is output to the power amplifier 4 [43 in FIG. 2].

The power amplifier 4 sends a drive current corresponding to the optimum operation amount to the robot, drives the motor of the selected axis, and controls the arm.

Next, positioning is completed at 11'! The verification is performed [44 in Figure 2], and if the process is completed, the process returns to the beginning. If not, check whether the sampling time is over [45 in Figure 2].
If not yet, wait. If the sampling time has ended, a new timer is started and the optimal operation amount for the next sampling time is calculated.

As described above, in this embodiment, the sampling time is selected depending on the number of moving axes, so the sampling time can be optimized. Therefore, unlike when the sampling time is set uniformly, time is not wasted, and the servo control becomes more efficient.

〔Effect of the invention〕

According to the present invention, an arm model with an optimal sampling time can be selected according to the number of moving axes of the robot, and digital control can be performed using the sampling time, so it is possible to obtain the highest control performance regardless of the number of moving axes. can.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a flow chart showing an embodiment of the present invention, and FIG. 3 is a diagram showing a conventional digital control device. In the figure, 1 is a robot, 2 is a digital control device,
3 is a mathematical model, 4 is a power amplifier, 5 is a control strategy management section, and 6 is an optimal operation amount calculation section. Figure 1

Claims (1)

[Scope of Claims] A mathematical model of an articulated robot, and means for calculating an optimal operation amount based on the mathematical model at each predetermined sampling time, A digital control system for a robot that controls an articulated robot includes means for determining the number and number of axes of joints to be controlled, means for selecting a sampling time corresponding to the number of axes to be controlled, and means for selecting a sampling time according to the number of axes to be controlled; A digital control device for a robot, comprising means for selecting a mathematical model according to a power axis and its number.