JPS63181011A - Control method for robot - Google Patents

Abstract

PURPOSE:To realize an operation at high speed and with resulting high acceleration deceleration, by calculating a speed pattern in which the minimum operating time can be obtained within a range where the effective torque of a motor goes less than rated torque based on the measured data of the torque of the motor, and controlling the motor based on the speed pattern. CONSTITUTION:The titled method is constituted in such a way that the speed and acceleration/deceleration (speed pattern) in which the minimum operating time within the range where the effective torque of the motor goes less than the rated torque can be obtained, are calculated, and the motor is controlled based on an obtained speed pattern. In such a way, since the driving of the motor is controlled by the speed pattern in which the minimum operating time can be obtained under a condition where the effective torque of the motor goes less than the rated torque at every operation, it is possible to always display the capability of the motor satisfactorily, and to operate the motor in the minimum time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of controlling a robot that is improved so that the robot can be operated at a speed and acceleration/deceleration that minimize the operating time.

(Prior Art) A typical industrial robot is composed of a rotating base, an arm, and a wrist, each of which is driven by a dedicated motor. On the other hand, the controller is equipped with a memory, a microprocessor, and a driver that directly controls each motor.The microprocessor retrieves the position information and operation program information stored in the memory, and processes this information. Based on this, a speed command is given to each motor via each driver to control the drive of the motor.

Conventionally, in such a motor control configuration, the maximum speed and maximum acceleration/deceleration of the motor are set to constant values, and a speed pattern is calculated based on these values to control the speed of the motor.

(Problems to be Solved by the Invention) Recent industrial robots are required to have high payload, high speed, and high acceleration/deceleration, and in order to meet these demands, large motors are required. tend to be adopted.

However, in conventional motor control methods, the maximum speed and maximum acceleration/deceleration are determined under the worst usage conditions, i.e.
The motor is set to a value that allows easy control of the motor in this case, based on the case where a product with the maximum weight among the payloads is to be transported.

Therefore, depending on the operating conditions, for example when transporting lightweight products, the motor torque may be kept lower than necessary, and in such cases it is possible to shorten the operating time in terms of performance. However, the problem is that the actual operating time becomes longer.

The present invention has been made in view of the circumstances listed in -1-.1-1 is that it is possible to always make full use of the motor's ability, and that speeds and speeds can be increased without increasing the size of the motor. The object of the present invention is to provide a control method for a robot that can achieve acceleration and deceleration.

[Structure of the Invention] (Means for Solving the Problems) The robot control method of the present invention is a robot that operates an arm by driving a motor in accordance with commands from a controller based on operation contents stored in a memory. Based on the measured data of the torque of the motor, calculate the speed and acceleration/deceleration (hereinafter referred to as speed pattern) at which the operating time is the shortest within a range in which the effective torque of the motor is equal to or less than the rated torque, and calculate the obtained acceleration/deceleration. The motor is characterized in that the motor is controlled based on the determined speed pattern.

(Function) According to the present invention having the second means, the drive of the motor is controlled in accordance with the speed pattern that minimizes the operating time under the condition that the effective torque of the motor is equal to or less than the rated torque for each operation. It is possible to always make full use of the motor's ability and operate it in the shortest possible time.

(Example) An example in which the present invention is applied to an articulated robot will be described below with reference to the drawings.

First, in FIG. S showing the overall configuration of the robot, first and second arms 3 and 5 are attached to a rotating base 2 provided on a fixed base 1.

A third arm is connected to the second arm 4, and a fourth arm is provided with wrist portions 6a on the first and third arms 3 and 5.
An arm 6 is attached. The above-mentioned turning base 2 is
Driven by a motor 7 via a speed reducer (not shown),
Further, the first and second arms 3 and 4 are rotated in directions of arrows 12 and 13 by ball screw mechanisms 10 and 11, which are rotated by motors 8 and 9, respectively, via a reduction gear (not shown). There is. And the wrist part 6a is
The rotating base 2 rotates and the first and second arms 3 and 4 rotate to move three-dimensionally. The robot configured in this manner is controlled by a controller 14.

This controller 14 has a memory 1 as shown in FIG.
5. It includes a microprocessor 16 and drivers 17-19. The motors 7-9 are controlled by drivers 17-19 based on position information from position detectors 7a-9a provided respectively. The drivers 17 to 19 control the motor 7 according to a speed command value given by the microprocessor 16 based on the contents stored in the memory 15.
Control the speed of ~9.

A method of calculating speed-related data to be stored in the memory 15 for speed control of the motors 7 to 9 will be described below. For convenience of explanation, we will explain the motor 8 that drives the first arm 3 and the fact that the first arm 3 normally starts and stops many times while the robot completes one task. However, for the sake of convenience, one operation from one activation to one stop will be described here.

That is, the memory 15 stores the motor 8 set to an appropriate value.
Maximum speed V MIIIX, maximum acceleration/deceleration α, acceleration/deceleration α0. The movement angle θ of one movement of the first arm 3 taught in advance is stored. Based on this stored content, the microcontroller uses the movement path information (hereinafter referred to as position information) of the taught movement stored in the memory 13 while holding the product to be actually conveyed in the wrist portion 5. A speed command is given to the driver 18 by the processor 16 and test driving is performed. Through this test drive, the torque of the motor 8 is measured by a torque detection means consisting of a current detection means provided in the driver 18, for example, and each torque during acceleration, constant speed running, deceleration, and stopping is measured by the microprocessor 16. The data is stored in the memory 15 via the computer. Note that when the motor 8 is stopped, a torque that rotates the ball screw mechanism 10 is applied due to the weight of the first arm 3 when the motor 8 is stopped. This refers to the torque generated in the motor 8 to prevent it from rotating.

Now, the acceleration torque T ao, the constant speed running torque T "0. The deceleration torque Tdo, the stopping torque Tho, and the maximum speed V MA stored in the memory 15 in this way are
X, maximum acceleration/deceleration α, acceleration/deceleration α0, and movement angle θ
In addition to the value t(,s+
The initial data is stored in the memory 15 with N set to (1), and based on this initial data, the speed and acceleration/deceleration of the motor 8 are sequentially changed within a range where the effective torque of the motor 8 does not exceed the rated torque. Then, calculate the operating time in each case.

This calculation is performed as shown in the flowchart of FIG. That is, first, following the flow shown by arrow A in FIG. Effective torque (root mean square) T
Find ra+s and operating time tc. This TrIIIS
and tC can be determined using the following formula.

tc -1a +tr +td +th However, Ta is acceleration torque, T is constant speed running torque, Td is deceleration torque,
Th is the torque at stop.

In addition, ta is acceleration time, tr is constant speed running time, td is deceleration time, and th is stopping time, which are the operating angle θ and speed V.
It can be determined from t and acceleration/deceleration αl.

Here, Ta acceleration torque, Tr constant speed running torque, Td
is the deceleration torque, and Th is the torque at stop, which can be determined by the following equation.

■Torque at stop Th - Th.

■Constant speed running torque Tr is defined as Tc (constant), which is the torque required to be applied to the arm for constant speed running.
It is expressed as r - Tc /μ, where μ is the efficiency of the reduction gear, so Tr = Te /μ - Tr.

becomes.

■The acceleration torque Ta is: θa is the angular acceleration). Since the increase/decrease in acceleration torque Ta is proportional to the angular acceleration, it becomes g. Therefore, Ta can be found as follows.

In this case, θa and θaO are α1. It can be found from α0.

(2) The deceleration torque Td can be expressed as CD' Td-Tr+-tdg. In the case of this embodiment, θd
--θa, therefore, Td can also be determined in the same manner as described above.

Once Trm and tC are obtained in the above manner, αi is sequentially subtracted from αi by a predetermined constant B (for example, about 1 × 0 of αi) according to the flow shown by the arrow in FIG. Then, the operation of calculating the effective torque T rlns and the operating time tc is repeatedly executed until T rms≦rated torque. When T rffls≦constant torque,
Next, a comparison is made between tcMIN and tc. Here t
If cs+N>tc, follow the flow shown by arrow C in Fig. 3 and change tc, Vi, and al to t CMIN-, respectively.
tc, VmVi, a-alt=stage setting.

Then, by further subtracting B from this α1, the effective torque T
The operation of calculating rffls and operation time tc is repeated. On the other hand, in the comparison judgment between tcMIN and tc, tc+
When +t+≦tc, according to the flow shown by arrow 2 in Fig. 3, a predetermined constant A is added to Vl, and it is determined whether the value is greater than VMX. i1ro,
Execute the motion shown in the flow shown by C or 2, and if the value is large, end the calculation there, and save V and α set in the flow shown by the last arrow C to the memory 15 as the maximum speed and maximum acceleration/deceleration in one motion. Remember.

Further, if tcMIN>tc, the operation shown by arrow C is executed again, and when tcM+N≦tc, the operation shown by arrow 2 is executed.

Note that during the execution of the above A11B and C flow-following operations, αi≦
If it becomes 0, add A to vl according to the flow shown by arrow H in FIG. 3, and then add A to vl.

The operations according to the flow shown in b or c are executed.

As described above, while changing the maximum speed V and acceleration/deceleration α, the maximum speed and acceleration/deceleration at which the operating time tc becomes the minimum are determined. Note that such calculations are performed by the controller 14.
It can also be executed by an external computer with an interface.

The optimum maximum speed and acceleration/deceleration as described in 1- below are calculated for each operation of each motor 7 to 9 and stored in the memory 15. Then, a speed command value is calculated for each operation based on this value, and the speed command value is given to the drivers 17 to 19 to control the motors 7 to 9 in an optimal operation pattern.

Figure 4 shows the relationship between movement amount, speed, and operation time.
This method calculates the acceleration/deceleration that results in the minimum travel time when the motor's effective torque is less than the rated torque, assuming the travel amount and speed are constant, and then calculates the operating time based on this and plots it for each speed. As is clear from FIG. 4, it is understood that there is a speed that provides the minimum travel time depending on the amount of travel.

As described above, the speed and acceleration/deceleration that minimize the operation time are set in consideration of the amount of ffi of the product actually transported by the robot for each operation, and the speed of motors 7 to 9 is controlled based on this. As a result, the takt time of the robot is shortened and the productivity of the robot is improved. Moreover, the torque of the motors 7 to 9 is not controlled so that it does not exceed the rated torque even temporarily, but the effective torque is controlled so that it does not exceed the rated torque. It is possible to drive the motors in the fully utilized state, and from this, it is possible to cope with dual high payloads and high speeds without making the motors 7 to 8 so large.

[Effects of the Invention] As is clear from the above explanation, according to the robot control method of the present invention, it is possible to achieve high speed and high acceleration/deceleration, shorten the operation time of the robot, and constantly operate the robot. Since the motor can be controlled to its full potential, it is possible to achieve the excellent effect of achieving the above-mentioned high speed and high acceleration/deceleration while preventing the motor from increasing in size as much as possible.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a flowchart of calculations for determining speed and acceleration/deceleration, and FIG.
FIG. 3 is a block diagram showing the control structure of the robot, FIG. 3 is a side view showing the schematic structure of the robot, and FIG. 4 is a characteristic diagram showing the relationship between speed and operation time. In the figure, 2 is a rotating base, 3 to 6 are first to fourth arms,
6a is a wrist part, 7-9 are motors, 10.degree. 11 is a ball screw machine tMs14 is a controller, 15 is a memory, 16 is a microprocessor, and 17-19 are drivers. Figure 1 14 Controller Figure 2 Figure 3121 Figure 4

Claims (1)

[Claims] 1. In a robot that operates an arm by driving a motor based on commands from a controller based on operation details stored in memory, the effective torque of the motor is below the rated torque based on measurement data of the torque of the motor. 1. A method for controlling a robot, comprising: calculating a speed pattern that results in the shortest operating time within a range of , and controlling the motor based on the obtained speed pattern.