JP3286842B2 - Flexible control device for robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible control device for a robot or the like, and in particular, it is possible to limit a generated force of a servomotor for driving a joint based on a force and a torque set value in a working coordinate system. Limiting the gain of the robot's flexible control device, especially the position / velocity control system, or limiting the generated force of the servomotor that drives the joint by the torque limit value, flexibly follows external force when applied. By controlling the gain of the flexible control device of the robot, and more particularly the position / velocity control system, or by limiting the generated force of the servo motor that drives the joint by torque control,
A robot flexible control device that changes the flexibility of a flexible control system in a device that flexibly controls a robot against external force. And a flexible control device such as a servo-controlled robot capable of interrupting or changing the work.

[0002]

2. Description of the Related Art One conventional robot is controlled by a position and speed control system as shown in FIG. When performing work that involves contact with the work with such a control system, if there is a work misalignment, a large torque is generated due to the action of the gain and integrator that are set large to increase rigidity. This causes an overload condition and makes it difficult to perform the work. Special mechanical jigs such as a float device and RCC that absorb the acting force for such problems,
A force control method using a force sensor has been performed [conventional example 1]. In recent years, as a method of performing flexible control without adding a special device to a robot, a method of lowering a servo gain as disclosed in JP-A-6-332538 [conventional example 2 / FIG. -20941 [Conventional example 3, not shown]
As disclosed in Japanese Patent Application Laid-Open No. H11-260, a system capable of setting softness in a working coordinate system is disclosed.

The conventional example 2 is a flexible servo control method that enables a driven body driven by a servo motor to be moved manually to avoid an obstacle. , Position gain Kp (110a),
The proportional gain Kv (112a) of the speed control loop is reduced according to the degree of softness set. Also, the output of the integrator 113 of the speed control loop is limited to the set clamp value (121) (shown in FIG. 16). As a result, even if the positional deviation increases, the torque command does not become an exceptionally large value, so that the driven body driven by this servomotor can be moved by human power. This is a technique that, when there is an obstacle in a moving path of a driven body, the obstacle can be moved by avoiding the obstacle by human power.

The prior art 3 is a flexible servo control method which enables the gain of a servo system of a robot incorporated in each axis to be changed by setting softness on work coordinates. In a control method of a servomotor controlled by a control system having a speed control loop, a softness designated on a working coordinate at which the servomotor is located is adjusted by a servo gain Kp for each axis of the servomotor.
(110a), Kv (112a), a servo motor is driven by the converted servo gains Kp, Kv, and a driven body driven by the servo motor can be manually moved.

Further, instead of reducing the loop gain, there is a flexible control system for a robot in which the posture is changed when an output force of a position / speed system is provided and an external force exceeding a certain level is applied [Conventional example 4, FIG. 16]. . In addition, literature "Impedance control of direct drive manipulator without using force sensor" Tachi, Sakaki, Journal of the Robotics Society of Japan, 7-3, p.
As described in p.172-184,1989, a position control loop, speed control loop, and acceleration control loop are provided independently,
In a control method in which the result of adding each of them is used as a torque command to a motor, an impedance control method in which mechanical rigidity, viscosity, and mass are adjusted by adjusting respective gains is shown [Conventional Example 5 / FIG. 17]. ].

Conventional Example 6 FIG. 18 shows a motor position control system which has been conventionally used in a robot controller. In the position control system, the speed control loop gain Kv and the position loop gain Kp are set as high as possible in order to perform positioning against friction and external force. Further, by placing an integrator in parallel with the proportional gain, control is performed to further enhance the characteristics. With such a control method, the servomotor can be accurately positioned at the target position even under the condition where external force acts. Instead of the conventional control method with high rigidity as described above,
As shown in FIG. 19, a control method in which the motor or a load coupled to the motor moves flexibly when a force acts on the servo system from outside by removing the integrator or limiting the integral value and reducing the control gain. Has been done.

Further, there is a control method as shown in FIG. 20 of the conventional example 8 which flexibly responds to an external force by limiting the output torque without changing the control gain. With the above-mentioned flexible control method, for example, in a robot, a force is applied to the robot from an external machine and the robot can receive it flexibly, or the robot grips and presses a part, It is used for operations such as preventing unnecessary force from acting when an object collides.

[0008] Then, as a conventional control method, the conventional example 2
As shown in FIG. 15 [JP-A-6-332538], a method is disclosed in which the output of the integrator of the speed control system is limited and the loop gain is reduced according to the set softness. In addition, there is a flexible control system for a robot in which the output of a position / velocity control system is limited instead of reducing the loop gain, and the posture changes when an external force exceeding a certain level is applied [Conventional example 6 / FIG. 17].

[0009]

However, the conventional example 1
The method of adding the dedicated jig and the force sensor shown in FIG. 14 (the jig and the sensor are not shown) has a problem that the cost increases. In addition, Conventional Example 2 and FIG.
In FIG. 16, a method for reducing the servo gain is used, but in these methods, it is necessary to adjust a plurality of servo gains while maintaining a certain relationship. Further, when the servo deviation increases, the generated torque of the servomotor increases proportionally, and therefore, it is impossible to cope with a case where the stroke of a machine or the like acting from the outside is large.

Further, in the conventional example 3 and FIG. 16, a method for controlling the flexibility in the working coordinate system is disclosed. However, it is necessary to obtain the gain by associating the displacement of the joint coordinate system with the displacement of the working coordinate system. Therefore, the computational relational expression is complicated and the computational load is large, and it is not possible to continuously obtain a gain with respect to a change in the posture of the robot. In particular, in the case of a robot posture in which the change rate of the correspondence relationship between the joint angle and the work coordinates is large, such as in the vicinity of a singular point, the computation load of the CPU is large, and it is not possible to perform real-time computation for the posture change of the robot. Since it is difficult to continuously calculate the gain, there is a problem that the softness of the robot may vary greatly depending on the posture of the robot.

Next, in the method of reducing the loop gain of the control system of the conventional example 2 and FIG. 15, it is possible to control rigidity and viscosity in the mechanical impedance when the robot is moved by an external force. It is not possible to reduce the mass of the robot arm that the robot originally has or the mass added to the robot tip. Therefore, the reaction force when the robot arm is accelerated by an external force cannot be reduced, and the flexibility of moving with a small force cannot be realized. The same applies to the method of providing the output limitation of the position / speed control system of the conventional example 6 / FIG.

Further, in the conventional example 5 and the method of Tachi and Sakaki in FIG. 17, it is not possible to easily shift between the conventional position control. That is, since the configuration of the control loop is different, it has been difficult to switch between the position control and the flexible control while maintaining the continuity of the state quantity. Then, in the systems of Conventional Examples 6 to 8 and FIGS. 18 to 20, there is no protection means in the case of being pushed from the outside and performing a displacement exceeding the allowable value. For this reason, for example, a robot has the following problems. A. The robot is pushed from the external device and moves out of the operation range, thereby causing obstacles such as collision with surrounding devices. B. When a heavy object exceeding the specified weight is gripped during handling, the object is deformed in the direction of gravity, causing the same problem as A.

The conventional examples 6, 7 and 8 have no means for taking the following measures to make the most of the flexible control. C. The handling object is determined based on the displacement caused by the weight in the handling, and the subsequent work plan is changed. D. Change the execution procedure of the work by detecting collision with the object. That is, there is no information for knowing that an abnormal state is caused by the applied force, information on how much force is being applied, and means for detecting how much from the target trajectory by the force. Was. Therefore, the robot is stopped when it is flexibly displaced by receiving an external force. It has been impossible to take measures such as stopping an external device or changing a motion plan of a robot or the like.

Further, in the method of reducing the loop gain of the control system of the conventional example 2 and FIG. 15 and the method of limiting the output of the position and speed control system of the conventional example 8 and FIG. When the robot touches the robot, is pinched between arms, or when the robot touches another object, the deviation between the command of the position / velocity control system and the detected value increases, causing the robot to move in a more dangerous situation. The operator was very difficult to escape from the dangerous state, causing damage to the robot itself and other objects.

Accordingly, the present invention provides a flexible control device for a robot which is capable of flexible setting of one variable with one degree of freedom and large displacement of a stroke, and which performs flexible control in a working coordinate system by simple coordinate conversion. The primary purpose is to provide. In addition, the present invention also provides a robot that flexibly follows an external force when an external force is applied thereto by limiting the gain of the position / velocity control system, or by limiting the generated force of a servomotor that drives a joint by a torque limit value. A second object of the present invention is to provide a robot flexible control device that obtains more flexibility in control.

Further, according to the present invention, when an external force is applied,
A flexible control device for a robot that flexibly follows that force, in particular, by controlling the gain of a position / velocity control system or controlling the torque to limit the generated force of a servo motor that drives a joint, makes the robot flexible against external forces. It is a third object of the present invention to provide means for controlling the safety and whether the work is being performed correctly.

Still further, according to the present invention, the safety of the worker and the robot can be maintained even when the worker comes into contact with the operating robot during the flexible control, is caught between the arms, or the robot comes into contact with another object. It is a fourth object of the present invention to provide a flexible control device for a robot which secures the robot.

[0018]

The present invention comprises the following means for solving the above problems. That is, the first
Means for controlling the torque of a servomotor that drives a joint of a robot, means for measuring a joint angle, and a coordinate system generally called Jacobian based on the measured joint angle information. A means for calculating a small displacement relationship between the two, a means for converting a limit value of a force or a torque set in a working coordinate system into a joint angle torque limit value by using a Jacobian transpose matrix, and using the torque limit value. Means for restricting the output torque of the robot by means of a robot. It is possible to set the flexibility of one variable with one degree of freedom and to make a large displacement of the stroke. A flexible control device for the robot that can perform the control is obtained.

In order to achieve the second object, there is provided means for changing a position control gain and a speed control gain in a motor control system, and an output of an integrator in a proportional integral control in a speed control loop is limited. A feedback control means for multiplying the acceleration of the motor by a constant to the torque command at the subsequent stage of the speed control gain multiplication to provide a new torque command, and a means for limiting the torque command to a constant value, In addition, a feedback control means that multiplies the acceleration of the motor by a constant is provided, and the output is used as a new torque command.When an external force is applied, a robot flexible control device that flexibly follows the force is used. can get.

In order to achieve the third object, the angle command value of the position control system is compared with the deviation of the current angle and the set value, and based on the result, the motor is stopped, a signal is output to the outside, and Having means for changing the operation plan of the servo system,
In addition, the method includes determining a deviation in the work coordinate system. In addition to changing the flexibility of the flexible control system, it is possible to make the coordinate system of the set value to be compared with the coordinate system of the work target the same. This makes it possible to obtain a flexible control device for a robot that can easily set a set value for comparison.

In order to achieve the fourth object, in a control system of a motor for driving a joint of a robot having a position control loop and a speed control loop, means for changing a position control gain and a speed control gain, And means for changing the position control gain and speed gain to different states based on the direction command information, the detection information, and the calculation result of the information, and the addition result of the proportional control and the output of the integrator. Means for limiting the torque command, and means for changing the torque limit based on the command information of position, speed, and direction, the detection information, and the calculation result of the information. The robot keeps the worker and the robot safe even if the robot touches the moving robot, is caught between arms, or the robot touches another object. Flexible control device is obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention comprises means for controlling a torque of a servomotor for driving a joint of a robot, means for measuring a joint angle of the joint, and the measurement. Means for calculating a minute displacement relationship between coordinate systems based on the information of the joint angle according to the above, and a limit value of a force or a torque set in a working coordinate system, and a joint angle torque limit value by using the minute displacement correspondence relationship. means for converting, the torque limiting means for limiting the output torque of the robot using said joint angle torque limit value, the torque limit hands
Torque compensation to compensate for gravity or friction torque at the previous stage
This is a flexible control device for a robot characterized by comprising compensation means, and by converting the force and torque in the working coordinate system into the limit value of the torque in the joint coordinate system,
It has the effect that a flexible motion can be performed with respect to a force greater than the limit value of the force working coordinate system acting from the outside.

The invention according to claim 2 of the present invention uses the command value of the joint angle of the control system of the servomotor for driving the joint of the robot, thereby obtaining the minute coordinates of the working coordinate system and the joint coordinate system. 2. A flexible control device for a robot according to claim 1, wherein a correspondence is obtained, and flexible control in a working coordinate system is enabled by simple coordinate conversion using information on a position of a joint angle. It has the action of:

According to a third aspect of the present invention, there is provided a flexible control device for a robot having a control system of a servomotor for driving a joint of the robot having a position control loop and a speed control loop. Means for limiting the output of the integrator in the proportional integral control, a torque limiter for limiting the torque command which is the result of addition of the proportional control and the output of the integrator, and detecting or calculating the rotational acceleration of the motor. Means, feedback control means for multiplying the acceleration of the servomotor by a constant after the torque limiter, and gravity or friction torque before the torque limiter.
And a torque compensating means for compensating for the above problem. This is a flexible control device for a robot, which has the effect of improving the flexibility of the robot.

The invention described in claim 4 of the present invention, a position control loop and speed control loop plurality Yes, the difference between the work coordinate system current values obtained from the current value of the servo motor and the target value in the working coordinate Means for comparing with a set value;
Claim from claim 1, characterized by comprising, a means for stopping the motion of the servo motor on the basis of the comparison result
3. The flexible control device for a robot according to any one of 3), which has an effect that a servomotor can be stopped based on a current value in a work coordinate system.

The invention described in claim 5 of the present invention, a position control loop and speed control loop plurality Yes, the difference between the work coordinate system current values obtained from the target value and the current value of the servo motor in the working coordinate 4. The apparatus according to claim 1 , further comprising: means for comparing with a set value; and means for outputting the result of the comparison from the servo device to an external device.
A flexible control device for the robot described in
Even in a control system having a plurality of position control loops and speed control loops, when the value of the position deviation is larger than the set value,
It has the effect of sending a signal to an external device using the input / output contacts of the robot (stopping the external device, etc.).

The invention described in claim 6 of the present invention, a position control loop and speed control loop plurality Yes, the difference between the target value and the work coordinate system current values obtained from the current value of the servo motor in the working coordinate 4. The apparatus according to claim 1 , further comprising: means for comparing with a set value; and means for changing a servo control process based on the calculation result.
A flexible control device for the robot described in
Even a control system having a plurality of position control loops and speed control loops has the effect of performing conditional branching of robot software based on information on position deviation.

According to a seventh aspect of the present invention, there is provided a means having a position control loop, capable of changing a position control gain and a speed control gain, position, speed and direction command information, detection information and the information. And means for changing the position control gain and the speed gain to different states based on the calculation result of (1).
A flexible control device for a robot according to any one of the above, and has an effect of ensuring the safety of a worker or a robot.

The invention described in claim 8 of the present invention, have a position control loop and speed control loop, and means for limiting the torque command is a sum of the output of the proportional control and an integrator, the position, velocity, And means for changing a means for limiting the torque command based on direction command information, detection information, and a calculation result of the information .
4. The flexible control device for a robot according to claim 3 , wherein the position control gain and the speed gain are changed from the command information, the detection information, and the calculation result of the information to further lower the torque command. It has the effect of keeping the safety of workers and robots.

According to a ninth aspect of the present invention, a means for compensating for gravity or friction torque is provided after the means for adding the proportional control and the integral control in the speed control loop. A robot control apparatus according to claim 7 or 8, wherein the robot is compensated for by gravity or friction torque to prevent the robot from falling in the direction of gravity even when the posture of the robot changes, and the robot is operated by an operator. When the robot touches or is caught between arms, or when the robot comes into contact with another object, it has the effect of changing the torque limit and ensuring the safety of the worker and the robot comprehensively. . Next, embodiments of the present invention will be described with reference to the drawings. The same reference numerals in the drawings denote the same members or corresponding members.

(Embodiment 1) In this embodiment 1, a minute displacement relationship between a joint and a work coordinate system is calculated from measurement information of a joint angle of a robot, and a joint angle limit value is obtained to limit an output torque. It is a means to do. That is, it can be said that this is a torque limiting method in the flexible control of the robot. FIG. 1 is a diagram showing a circuit configuration representing one concept of an operation according to the first embodiment of the present invention. Also, FIG.
FIG. 5 is a diagram showing a circuit configuration representing another concept of the operation in the first embodiment of the present invention. 1 and 2, 100 is a first axis control system, 200 is a second axis control system, 300 is a third axis control system, n00 is an nth axis control system, 101a is a torque command, 101b is a torque command, 102 Is a torque limiter, 103 is a corrected torque command, 104 is a servo amplifier (torque control), 105 is a servomotor, 106 is a position detector, 107 is work coordinate force / torque limit setting means, and 108 is a transpose matrix J ^{T of} Jacobian. Calculation means.

Hereinafter, a specific embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram illustrating a specific circuit configuration. In FIG. 3, reference numeral 110 denotes a position control gain [Kp].
Circuit, 111 is a speed control gain [Kv] circuit, 116 is a torque limiter, 117 is a gravity compensator, 118 is a torque conversion constant circuit, 119 is a mechanical system such as a robot [J is inertia, s
Is a Laplace operator, D is a coefficient of kinetic friction], and 120 is an integration circuit [showing the relationship between speed and position].

FIG. 3 in the first embodiment shows a control block diagram in which the flexible control system of the present invention is applied to a conventional position control system [FIG. 14 and Conventional Example 1]. In the inner loop of the position control, a proportional integral control is usually performed, but a force such as gravity that acts constantly is compensated by a static force compensating element. In the normal position control state, displacement is unlikely to occur due to externally applied force due to the operation of the position control loop and the speed control loop. This is because the motor torque is generated by multiplying the gain by a set gain with a large deviation from the command value by an externally applied force.

Here, by limiting the generated torque at the stage of the torque command, the robot can perform a flexible operation with respect to an externally applied force. That is, when a torque larger than the limiting torque acts from the outside, the joint of the robot starts to move. Further, the torque limit value set here is a torque limit value in the joint coordinate system. Therefore, the limitation of the force at the tip working position changes depending on the posture of the robot. Therefore, the current state of the robot is detected, the correspondence between the joint coordinate system generally called Jacobian and the minute displacement of the work coordinate system is determined based on the value, and the transposed matrix is calculated to calculate the transposed matrix. It is possible to calculate the torque limit value in the joint coordinate system from the force limit value.

For example, the equation for calculating the transposition of the Jacobian in a robot having six degrees of freedom is represented by the following equation (1).
It is expressed by equation (4).

(Equation 1) By calculating the equations (1) and (4) with respect to the change in the posture of the robot and constantly obtaining the limit value of the joint torque, the force and torque shown in the equation (2) can be obtained in the entire operation range of the robot. The flexible control of the robot having the limit value can be performed. Equation (1) is a value that changes depending on the posture of the robot, and may show a rapid change in the vicinity of a singular point. In general, the value of each element depends on the sampling speed of the CPU that performs servo computation. The change is slow in comparison. Therefore, the calculation load of equation (1) can be kept small, and real-time calculation accompanying a change in the posture of the robot can be performed.

The flexibility in the working coordinate system is determined only by the limit value of equation (2). That is, one for one degree of freedom
Flexibility can be controlled by determining the number of variables. Further, since the force and torque generated by the robot are not proportional to the displacement, the robot can flexibly change even when the stroke of a machine acting externally is large.

(Embodiment 2) Embodiment 2 of the present invention is a system in which an acceleration control loop is further added to the conventional flexible control system. Embodiment 2
Is a flexible control system in which an acceleration control loop is added to, for example, Conventional Examples 2 and 15 or Conventional Examples 4 and 16. FIG. 4 is a block diagram showing a schematic circuit configuration of the first means of the second embodiment.

In FIG. 4, reference numeral 20 denotes a flexible control system (position / velocity control system); 114, an external force; 119a, a mechanical system such as a robot;
120a is an integration circuit, 122 is an acceleration calculator, 124 is a rotational acceleration feedback gain [J '] circuit, and 125 is speed detection
(Operation) circuit, 126 is a position detector. The first here
Means means for controlling the position control gain,
Feedback control with means that can change the speed control gain, limiting the output of the integrator in the proportional integral control in the speed control loop, and multiplying the motor acceleration by a constant to the torque command that is the subsequent stage of the speed control gain multiplication Means is provided and its output is used as a new torque command.

In the second means (FIGS. 5 and 6), the torque command at the subsequent stage of the speed controller is limited to a constant value in a motor control system constituting a control loop similar to the first means. Means is provided, and feedback control means for multiplying the acceleration of the motor by a constant is provided, and its output is used as a new torque command. 5 and 6, reference numeral 115 denotes a differentiator [speed detecting means], 121 and 121a denote torque limiters, and 127 denotes a torque limiter.
Is an acceleration detector, and 128 is an encoder. In the above means, an integrator for compensating gravity and friction is used, and its value is limited to the extent that flexibility is not impaired. However, the limit of the integral value may be zero if it is compensated by gravity calculation or is negligible. With the above-described means, the acceleration can be directly detected by a detector, or can be obtained from a difference between position detectors such as an encoder.

The gravitational torque is calculated by an operation using parameters such as the mass and the position of the center of gravity of the robot, and is compensated by adding it to the final torque command output to the amplifier. Hereinafter, a circuit configuration according to the second embodiment of the present invention will be described with reference to FIGS. That is, FIGS. 5 and 6 both show a specific embodiment of the second method. 5 shows a case where a rotational acceleration detector of a motor shaft is used as an acceleration detecting means, and FIG. 6 shows a means for calculating an acceleration from a position detector by calculation. An example is shown in which the present invention is applied to the first axis of a scalar type robot that operates in the horizontal direction with two degrees of freedom as a target robot. A similar control system can be configured for the second axis.

It is now assumed that the output of the motor position / speed controller is zero. In FIGS. 5 and 6, it is assumed that a torque of T is acting as an external force, and the inertia of the motor and the arm is J. When the feedback gain of the rotational acceleration of the control system is J ′ and the generated acceleration is α, the following equation (5) is established. α = T / (JJ ′) (5) That is, the apparent inertia is reduced more than the original inertia due to the external force. Here, the delay in the output of the acceleration detector and the output of the amplifier is assumed to be negligible, but a slight delay does not significantly affect the intended inertial fluctuation.

Next, how to determine the feedback gain J 'will be described. In the case of a two-degree-of-freedom robot, the inertia seen from the first axis changes due to the movement of the second axis. As a result, the value of the actual inertia J of the first axis fluctuates. However, the amount of inertia reduction due to the control is determined only by the feedback gain of the acceleration. Is determined. That is,
J ′ is determined so that the value of JJ ′ does not become a negative value and the loop gain of the speed control system does not vary as much as possible. Further, in order to maintain a constant inertia irrespective of the posture of the robot, the apparent inertia can be maintained at a constant value by changing J ′ in accordance with the motion of the robot.

As described above, the apparent inertia when an external force acts can be controlled to be small, and the flexibility is greatly improved as compared with the conventional flexible control. The fact that the apparent inertia can be controlled to be small with respect to the external force means that the acting force when the robot collides with a surrounding object or the like becomes small. For this reason, it is also possible to improve safety during robot control. Moreover, since the structure of the control system does not basically replace the conventional position / velocity system, the structure of the control system itself is changed even when shifting from the flexible control system to the position control system and from the position control system to the flexible control system. No need.

Therefore, even when the control system is shifted, the control amount is continuously changed, so that the robot arm is not accompanied by sudden and discontinuous movement. Describing a method of detecting acceleration, a rotational acceleration sensor directly connected to a motor can be cited as a direct detection method as shown in FIG. It is also possible to obtain the output of the multi-axis translational acceleration sensor attached to the robot by decomposing the output in the rotation direction.

As a method other than the acceleration detector shown in FIG. 6, the following method can be considered. 1) Differentiation of a speed sensor such as a tacho generator 2) Differentiation of an encoder signal after F / V conversion 3) Difference of an encoder signal Generally, it was difficult to obtain a good acceleration signal. , The multipoint difference of the signal,
By using a pseudo-differentiator or the like having a limited frequency band, it has become possible to obtain an acceleration signal with good accuracy and responsiveness.

In the above-mentioned robot, an example is shown in which the present invention is applied to a scalar type robot that moves in the horizontal direction. If the robot has a motion component in the direction of gravity, the component in the direction of gravity is calculated as shown in FIG. Compensation, and
A flexible control system can be configured by compensating the friction by detecting the speed. The above has described the flexible control method of the two-axis SCARA robot. However, the present invention can be similarly applied to an articulated robot having three or more degrees of freedom.

(Third Embodiment) In a third embodiment, a position deviation in flexible control is monitored, and danger avoidance and external force monitoring are performed based on an emergency stop of a robot, information output to an external device, a change in a work plan, and the like. It is a means that enables control. One example of the third embodiment of the present invention will be described with reference to FIG. FIG. 7 shows one of the motor control systems.
FIG. 3 is a block diagram illustrating a circuit configuration indicating an axis or one direction of a working coordinate system. In FIG. 7, 129 is a position deviation,
130 is a work coordinate system set value, 131 is comparison means, 132 is means for performing a brake circuit, external output, work plan determination, and the like.

Here, it is assumed that the flexible control as described in the section of the prior art is performed. That is, the position control gain,
It is assumed that the speed control gains Kp and Kv are reduced or the torque is limited. Thereby, the posture of the robot changes according to the force applied from the load side of the robot. This is from the position command of the robot control system,
This means taking the position of the displaced robot. Therefore,
The deviation amount can be obtained from the deviation between each servo motor angle and the command value.

In the above description, the displacement is considered as the displacement of the rotation axis. 1) Work coordinate system servo, 2) Command value before forward conversion and reverse conversion of joint angle, or 3) Joint angle and work coordinate The deviation from the command value in a coordinate system other than the joint coordinate system can also be obtained by using the correspondence (Jacobi matrix) of the small displacement of the servo. By comparing the deviation obtained as described above with a predetermined set value, it is determined whether or not the vehicle is in a safe operation state. Large when the value of the deviation is compared with a set value is not determined to secure performs the following have not <br/> Re or treatment.

Depending on the type of work, an emergency stop of the robot, a signal that sends a signal to an external device using the input / output contact of the robot (stops the external device, etc.),
Some robots perform conditional branching of robot software based on deviation information. In particular, if no problem occurs, the operation shifts to a normal operation. In addition to the above-described determination of abnormality, the force acting on the tip of the robot is estimated based on the information of the deviation, the handling object is selected, and the operation pattern of the robot is changed by the grasped object. Perform processing according to external force.

FIG. 8 shows an example of a circuit configuration of a control system which applies the present invention to a multi-degree-of-freedom robot and monitors deviations of a plurality of coordinates in a working coordinate system. In FIG. 8, 133 is an inverse conversion circuit, 134 is information from a plurality of other axes, and 135 is a forward conversion circuit. FIG. 8, which shows another example of the third embodiment of the present invention, shows that when a deviation is obtained in the working coordinate system, a servo system of the working coordinate system is configured and a method for obtaining the deviation can be most easily configured. Shows a configuration using a joint position servo system most commonly used in industrial robots.

In FIG. 8, the work coordinate system position command is usually set in an orthogonal coordinate system based on the base of the robot, and some deviations between the translation amount and the posture amount are compared with set values. Depending on the result, the following processes 1) to 3) are selectively performed, and a plurality of operations are performed simultaneously. 1) Emergency stop by brake of each axis of robot 2) Signal output to external contact 3) Branch of work plan based on software

FIG. 9 shows an example in which the work plan is changed by software. After performing the work by the position control [Step 1], the operation is shifted to the flexible control [Step 2].
3] The servo deviation during the flexible control is monitored [Step 4]. If the deviation (XERR) is larger than the set value (setX), it is determined that an abnormal state has occurred, such as a collision with an object [Step 8], and the initial posture is returned [Step 9]. When the work is performed normally [Step 5], that is, when no excessive deviation occurs [Step 5], the process moves to the next scheduled work [Steps 6 and 7].

(Embodiment 4) In Embodiment 4, in the flexible control of a robot, an abnormality such as contact or pinching of the robot is detected from a control state quantity, and a control gain and a torque limit value are changed and reduced. It is a means that enables escape by human power and compensates for gravity and friction. FIG. 10 is a block diagram showing a basic configuration according to Embodiment 4 of the present invention. In FIG.
11 is a position detection value, 20 is a flexible control system (position / velocity control system),
21 is a control state quantity, 30 is a state determination means, 31 is a flexibility set value, 117a is a gravity compensation value, and 117b is a friction compensation value. Hereinafter, the circuit configuration of the fourth embodiment of the present invention will be specifically described with reference to FIGS.
This will be described with reference to a block diagram shown in FIG.

FIG. 11 shows a position control gain,
An apparatus using means for changing a speed control gain,
FIG. 12 shows a system using a means for controlling a torque command which is a result of addition of the proportional control and the output of the integrator in the flexible control system. In FIG. 11, a position command input from a higher-level controller (not shown), a position detection value detected by a position detector 128 provided in each drive portion or each joint portion of the robot, and a speed detection through a differentiator 115. A torque command (generated torque) of the motor is calculated in the flexible control system 20 based on the value. 22a is a flexibility setting device, 136 is a gravity compensator, and 137 is a friction compensator.

In order to perform ordinary flexible control, the flexibility setting unit 22a calculates minimum position control gain setting values and speed control gain setting values required for normal operation of the arm of the robot 105, and changes the values. The position control gain 110a and the variable speed control gain 111a are set. Here, the torque command, which is the output of the proportional control in the speed control loop, is calculated in the gravity compensator 136 from the distance of each joint center from the position of each joint and the center of gravity of each arm and the mass of each arm. By adding the compensation torque of gravity acting on each arm and the compensation torque of friction acting on the driving portion of each joint calculated in the friction compensator 137 from the detected speed value of each joint, the output from the flexible control system is obtained. The torque command to be issued can be made smaller.

The torque command after the addition is transmitted to the servo amplifier 10.
The robot 105 is amplified and driven by the robot 105. Here, a position deviation, a speed detection value, and a control state amount in the flexible control system 20 are calculated.
The differential value of the speed deviation is constantly monitored by the flexible setting device 22a. If it is determined that the robot operation is abnormal, the position control gain setting value and the speed control gain setting value are set to the minimum value or zero, and the variable position control is performed. Gain 110a, variable speed control gain 11
This is the configuration to set them in 1a.

The determination flow of the control system configured as described above will be described with reference to FIG. For example, when the arm of the robot 105 comes into contact with the worker or other objects, or when the worker is
5, the posture of the robot 105 begins to deviate from the position command, the position deviation increases [Step A], the speed detection value decreases [Step B], and the sign of the differential value (acceleration) of the speed deviation becomes negative. [Step C] is as follows. At this time,
The position deviation and the detected speed value become larger than a predetermined specified value [YES in step A], the detected speed value becomes less than the specified value [YES in step B], and the differential value of the speed deviation becomes negative. If it has become [YES in step C], it is determined that an abnormality has been detected, and the position control gain set value and the speed control gain set value are set to the minimum value or zero so as to reduce the flexibility of the flexible control system, and the variable position control gain is set. 110a and the variable speed control gain 111a are set.

As a result, the torque command of the motor from the flexible control system becomes minimum or zero, and the robot comes to rest while maintaining the posture at the time of the abnormality determination. At this time, since the gravitational torque and the friction torque are added to the torque command, the robot 105 does not fall down due to gravity, so that the operator can operate the robot 105 by input after the robot 105 stops. Become.
When the torque limiter 121 is provided in the flexible control system 20a in FIG. 12, the same effect as in FIG. 11 can be obtained.

By the way, the relationship between the embodiments of the present invention described above will be additionally described. The first embodiment is a means having a basic concept of flexible control of a robot facing the second conventional example [Japanese Patent Laid-Open No. 6-332558], and the second embodiment is applicable to the first embodiment, the second conventional example, and the like. Embodiment 3 is applied to Embodiment 2 and the like,
Embodiment 4 is applicable to Embodiments 1 to 3 and Conventional Example 2.

[0061]

As described above, according to the present invention, the following effects can be obtained. That is, there is an effect that flexible control in the work coordinate system is enabled by simple coordinate conversion using information on the position of the joint angle. In this case, it is possible to set one variable with one degree of freedom, and since the conversion formula itself is a simple formula, the calculation load is small and the calculation of the working coordinate system can be executed in real time. Further, since the constant reaction force of the robot is constant, the posture of the robot can be largely changed with respect to a force equal to or greater than the generation limit value.

Further, by applying the feedback of the acceleration information to the flexible control, the inertia can be compensated and the flexibility can be further increased. In addition, since the basic configuration of the conventional control system is maintained, the transition between the position control system and the flexible control is easy. As a result, during flexible control, the robot can be easily moved by the force of the machine or manually, and there is no large force applied to the target object even when the robot collides with the surrounding object, which is not possible with conventional robots Has characteristics.

When flexible control is performed by the robot according to the present invention, when an external force is applied, the robot is greatly deformed, and can easily perform processing in the event of an abnormality such as slipping out of the operation area or colliding with an object during trajectory control. become. In addition, work that conventionally required a sensor, such as changing work content according to an external force, can be performed without using a sensor.

Further, according to the flexible control method of the present invention, the change in the state of the robot operation is determined from the control state amount in the flexible control, and the flexibility of the flexible control system is changed. Even if the worker comes into contact with another object or is caught between arms, the robot stops immediately and the force generated by the motor is released, which has the special effect of ensuring the safety of the worker and the robot. Can be.

[Brief description of the drawings]

 1

FIG. 1 is a diagram showing a circuit configuration representing one concept of an operation according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration representing another concept of the operation in the first embodiment of the present invention.

FIG. 3 is a block diagram showing a specific circuit configuration according to the first embodiment of the present invention;

FIG. 4 is a block diagram showing a basic configuration according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing one specific circuit configuration according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing another specific circuit configuration according to the second embodiment of the present invention.

FIG. 7 is a block diagram illustrating functions according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing a specific circuit configuration according to a third embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of a specific circuit configuration according to the third embodiment of the present invention.

FIG. 10 is a block diagram showing a basic configuration according to a fourth embodiment of the present invention.

FIG. 11 is a block diagram showing one specific circuit configuration according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram showing another specific circuit configuration according to the fourth embodiment of the present invention.

FIG. 13 is a flowchart showing a condition determination according to the fourth embodiment of the present invention.

FIG. 14 is a block diagram showing a circuit configuration of Conventional Example 1.

FIG. 15 is a block diagram illustrating a circuit configuration of a second conventional example.

FIG. 16 is a block diagram showing a circuit configuration of Conventional Example 4.

FIG. 17 is a block diagram illustrating a circuit configuration of a conventional example 5.

FIG. 18 is a block diagram showing a circuit configuration of Conventional Example 6.

FIG. 19 is a block diagram showing a circuit configuration of a conventional example 7.

FIG. 20 is a block diagram illustrating a circuit configuration of a conventional example 8.

[Explanation of symbols]

11 Position detection value 20,20a Flexible control system (Position speed control system) 21 Control state quantity 22a, 22b Flexibility setting device 30 State judgment means 31 Flexibility setting value 100 First axis control system 200 Second axis control system 300 3-axis control system n00 n-axis control system 101a Torque command 101b Position command 102,121,121a Torque limiter 103 Corrected torque command 104 Servo amplifier (torque control) 105 Servo motor 105a Robot 105b, 106 Position detector 107 Working coordinate force / torque limit computing means 109 a position control system 110 position control gain transposed matrix J ^T setting means 108 Jacobian [Kp] circuit 110a variable position control gain [Kp] circuit 111 speed control gain [Kv] circuit 111a variable speed control gain [Kv] circuit 112 Proportional calculator 113 Integrator 114 External force 115,115a Differentiator [speed detection means s is Laplace operator] 116,121,121a Torque limiter 117 Gravity compensator 118 Torque conversion constant circuit 119,119a Robot, etc.械系 [J is inertia, D
Is the dynamic friction coefficient] 120,120a Integrating circuit 122 Acceleration (computation) circuit 123 Acceleration control gain [Kα] circuit 124 Rotational acceleration feedback gain [J '] circuit 125 Speed detection (computation) circuit 127 Acceleration detector 128 Encoder 129 Position deviation 130 Work Coordinate system set value 131 Comparison means 132 Brake circuit / external output / work plan judgment means 133 Inverse conversion circuit 134 Information from multiple other axes 135 Forward conversion circuit 136 Gravity compensator 137 Friction compensator

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G05D 3/00-3/20 G05B 11/00-13/04 G05B 19/18-19/46 B25J 1 / 00-21/00

Claims (9)

(57) [Claims] A means for controlling a torque of a servomotor for driving a joint of the robot; a means for measuring a joint angle of the joint; and a coordinate system based on information of the joint angle based on the measurement. Means for calculating a minute displacement relationship, means for converting a limit value of force or torque set in the working coordinate system into a joint angle torque limit value by using the minute displacement correspondence relationship, and using the joint angle torque limit value. Torque limiting means for limiting the output torque of the robot by means of
A flexible control device for a robot , comprising: torque compensating means for compensating . 2. The minute correspondence between the working coordinate system and the joint coordinate system is obtained by using a command value of the joint angle of a control system of a servomotor that drives a joint of the robot. Item 4. A flexible control device for a robot according to Item 1. 3. A flexible control device for a robot having a servomotor control system for driving a joint of a robot having a position control loop and a speed control loop, comprising: an output of an integrator in a proportional-integral control in the speed control loop. Means for limiting a torque command which is a result of the proportional control and the output of the integrator; means for detecting or calculating the rotational acceleration of the motor; and Feedback control means for multiplying the acceleration of the servo motor by a constant, and compensation for gravity or friction torque at a stage preceding the torque limiter.
A flexible control device for a robot , comprising: a compensating torque compensating means . 4. A position control loop and a speed control loop.
If there is more than one target value in the work coordinates and the current value of the servomotor
Compare the difference from the current value of the work coordinate system
Means for stopping movement of the servomotor based on the comparison result.
4. A means according to any one of claims 1 to 3, further comprising:
A flexible control device for a robot according to any one of the above. 5. A position control loop and a speed control loop.
Multiple values are obtained from the target value in the work coordinates and the current value of the servo motor.
To compare the difference from the current value of the working coordinate system with the set value.
And a means for outputting the comparison result from the servo device to an external device
Claim from claim 1, characterized in that with a, the 3 Noise
A flexible control device for a robot according to any one of the above. 6. A position control loop and a speed control loop.
Multiple values are obtained from the target value in the work coordinates and the current value of the servo motor.
To compare the difference from the current value of the working coordinate system with the set value.
Step and means for changing servo control processing based on the operation result
Claim from claim 1, characterized in that with a, the 3 Noise
A flexible control device for a robot according to any one of the above. 7. A means having a position control loop and capable of changing a position control gain and a speed control gain.
And command information and detection information of position, speed, and direction, and
The position control gain and the speed gay are calculated based on the calculation result.
Claims and means that can alter the in to another state, further comprising a claim, wherein 3 Noise
A flexible control device for a robot according to any one of the above. 8. A torque command as a result of adding a position control loop, a speed control loop, a proportional control, and an output of an integrator.
Means for limiting , command information and detection information of position, speed and direction, and
The means for limiting the torque command is changed based on the calculation result.
And means capable of being converted.
A flexible control device for a robot according to any one of the above. 9. Proportional control and integration in the speed control loop
Compensate for gravity or friction torque after control summing means
7. The method according to claim 7, further comprising:
9. The flexible control device for a robot according to 8.