JPH08278822A - Impedance control method - Google Patents

Abstract

PURPOSE: To simultaneously control the finishing state and deformation of an operation object by constituting the processes of the contact and deformation of a controlled system and the operation object as a machine impedance model and controlling a deformation process. CONSTITUTION: The model of the contact process of the controlled system and the operation object and the deformation process of the operation object are constituted as the machine impedance model for which the position and speed of the controlled system to the operation object are amounts relating to balance. Then, a system 7 provided with the controlled system and the operation object detects force F applied to the operation object by the controlled system and the position X and the velocity V of the controlled system to the operation object, inputs the target position and target velocity of the controlled system to the operation object and controls the position and the velocity. In this case, the target velocity Vd and target displacement Xd are respectively the solutions of the relocity and displacement of the machine impedance model and are the parameters of the velocity and the displacement to be obtained by the sliding part of the system 7 and target force Fd is the parameter of the force applied to the operation object by the controlled system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external force which is a force applied to a work object by a controlled object or a force which the work object applies to a controlled object, a rigidity which is hardness of the controlled object, and a damping of the controlled object. The first edition of the first edition was issued on November 25, 1988 by Corona Co., Ltd., with parameters such as viscosity, inertia of mass of controlled object, position, velocity and acceleration of controlled object or work object. 1 of the basic theory of robot control of computer controlled mechanical system series 10
Mechanical impedance described on page 80,
By cooperatively controlling the contact process, which is the process in which the control target and the work target contact with a force with arbitrary rigidity and arbitrary viscosity, the hardness of the work target, the damping of the work target, and the control target are The present invention relates to an impedance control method for cooperatively controlling a deformation process, which is a process of deforming a work target by a force applied to the work target.

Specifically, the controlled object is controlled by the force feedback from the force sensor or the load cell, the mathematical model of the mechanical impedance, and the arbitrary force applied by the controlled object such as the processing machine to the work object such as the work. The acceleration to be obtained is obtained, and the velocity and position to be obtained by the controlled object are obtained from the acceleration.Feedback of the position from the position detector or velocity feedback by the velocity detector and the mathematical model of the deformation process are necessary for the desired deformation. Seeking power,
The speed and position of the controlled object are obtained, and the force causing the deformation is obtained from the deformation process, the difference between the force necessary for the deformation and the force causing the deformation, and the speed and the speed detector to be obtained by the controlled object. From the difference in speed due to, and the difference between the position to be obtained by the controlled object and the position by the position detector, a contact model that is a relative rigidity and viscosity relationship between the controlled object and the work object is obtained, and the mechanical impedance and The present invention relates to a control method for controlling a contact based on the contact model and controlling a control target so that a deformation of a work target is in a desired state.

[0003]

2. Description of the Related Art As a system disclosed in the prior art, in a system for detecting a force acting on a work object and controlling the position of a control target based on the detected force, a parameter relating to compliance and a compliance Of the control target position in the world coordinate system is generated by specifying a quantity related to the balance of the control target and a parameter related to the specified compliance and a quantity related to the force. Converted to the trajectory of the position of the target, from the trajectory of the position of the controlled object in the coordinate system, to generate the trajectory of the velocity and the acceleration of the controlled object in the coordinate system, the position of the controlled object in the unique coordinate system, In order to follow the trajectory of speed and acceleration, position control of the same control target is performed, and compliance control is improved. It is possible to reduce the control, and the compliance control when the speed is comparatively slow in the industrial manipulator with a high position rigidity by the servo is possible.By freely setting the rigidity, which is one of the parameters used for the compliance control, Japanese Patent Publication No. 6-83976 discusses a control method relating to compliance control for performing an assembly work that requires various force adjustments.

Further, the deburring tool is regarded as a rigid body, the equation of motion of the tool is determined using the compliance mechanism as a model, the position and speed of the tool are determined by a position detector and a speed detector, and the force acting on the tool is detected. Of the parameters of the equation of motion, inertia, viscosity, and rigidity are arbitrarily determined, and the position, the velocity, and the force are substituted into the equation of motion, and the equation of motion is the position or velocity that is a control parameter, or A virtual compliance control method concerning a control method for solving a force, controlling a robot by using a solved control parameter as a target value, and performing deburring work by the robot, is published in January 1993, Journal of the Robotics Society of Japan, Volume 11, No. 1. Are discussed in.

Furthermore, in drawing rolling, in order to control the wall thickness with high accuracy, when rolling a raw pipe by a continuous multi-stage rolling mill, the outer diameter and wall thickness of the pipe before and after drawing rolling in each stand, and Based on the target outer diameter and wall thickness of the finished pipe,
The maximum tensile coefficient that can be physically added is calculated for each stand, and the outer diameter and wall thickness of the pipe before and after drawing and rolling at each stand during the first rolling, the rotation speed of the roll, and the actual outer diameter and actual meat of the finished pipe. Based on the thickness, determine the actual tension coefficient actually added for each stand.For stands whose actual tension coefficient exceeds the maximum tension coefficient, modify the actual tension coefficient to be less than or equal to the maximum tension coefficient. JP-A-05-237532 discloses a wall thickness control method for a squeezing and rolling machine, which obtains and sets an actual tensile coefficient for each of the other stands so that a finished pipe having a target wall thickness can be obtained based on the maximum tensile coefficient. There is.

[0006]

SUMMARY OF THE INVENTION The above prior art is based on the drawing of the work object by the finish condition of the work object due to the rigidity and viscosity of the control object viewed from the work object, or the force applied by the control object to the work object. It is possible to control any one of the adaptation to the distortion with respect to the dimension or the deformation of the work object due to the force that the control object applies to the work object, but it is impossible to control all of them. It is not sufficient when deforming a work object that requires both finish and adaptation to distortion.

An object of the present invention is to provide a finish of a work object based on the rigidity and viscosity of the control object viewed from the work object,
It is an object of the present invention to provide a method of adapting to a distortion of a work object with respect to a drawing dimension by a force applied to a work object by a controlled object and simultaneously controlling deformation of the work object due to a force applied by the controlled object to the object.

[0008]

In order to solve the above-mentioned object, a force applied by a controlled object to a work object, a position and a speed of the controlled object with respect to the work object are detected, and the controlled object with respect to the work object is detected. Enter the target position and target speed of
In the system capable of controlling the position and the velocity, the controlled object specifies a parameter related to the mechanical impedance so that the controlled object has a specified mechanical impedance, the parameter related to the specified mechanical impedance, a detected force, and Solving the equation of motion in the coordinate system of the controlled object, including the force to be corrected and the force to be corrected, to obtain the target position and the target velocity of the controlled object with respect to the work object, which satisfy the equation of motion, and the target position and A main control system for force control is configured such that the target speed is input to the system, the position and speed are controlled, and the force applied by the control target to the work target becomes the target force. And the model of the contact process of the work object, and the deformation process of the work object, the position and speed of the controlled object with respect to the work object Configured as mechanical impedance models that quantity related balance, to proceed as deformation process is specified, for executing the contact process,
Set the parameters of the mechanical impedance model,
Specified parameters, the position and speed of the controlled object with respect to the work object and the target position and target speed are input to the mechanical impedance model, and the force to be corrected is obtained as an output,
The impedance control method is characterized in that the force to be corrected is input to a main control system and the system is controlled so that the deformation process of the work object proceeds as specified.

[0009]

According to the present invention, the force feedback from the force sensor or the load cell, the mathematical model of the mechanical impedance, and the arbitrary force applied by the control target such as the processing machine to the work target such as the work are controlled by the control target. The acceleration to be obtained is obtained, the speed and position to be obtained by the controlled object are obtained from the acceleration, and speed control or position control is performed to adapt to the distortion of the work object due to the force applied to the work object with respect to the drawing dimension. The position feedback from the position detector or the velocity feedback from the velocity detector, and the force necessary for the desired deformation from the mathematical model of the deformation process are obtained. Determining the force causing the deformation, the difference between the force required for the deformation and the force causing the deformation, and the speed that the controlled object should obtain. From the difference in speed due to the speed detector, and the difference between the position to be obtained by the controlled object and the position due to the position detector, a contact model that is a relative rigidity and viscosity relationship between the controlled object and the work object is obtained, and The work object is controlled by controlling the contact based on the mechanical impedance and the contact model to compensate for the finish condition of the work object due to the rigidity and viscosity of the control object viewed from the work object, and by the force applied by the control object to the work object. By simultaneously compensating for the deformation of the work object, the finished condition of the work object due to the rigidity and viscosity of the control object seen from the work object and the distortion of the work object against the drawing dimension due to the force applied to the work object by the control object The adaptation and the deformation of the work object due to the force exerted by the control object on the work object are simultaneously compensated.

[0010]

Embodiments of the present invention will now be described with reference to the drawings by taking deburring work as an example. FIG. 2 is a one-dimensional dynamic model for explaining the present invention. The numbers and symbols in the figure indicate mechanical elements and physical quantities.

The sliding portion 1 having a mass of 1 / KI, which is one of the controlled objects, slides in the direction indicated by displacement X in the figure. The sliding portion 1 is fixed to the dashpot 2 having a viscosity Cd.
The dashpot 2 is fixed in series with a spring 3 having a rigidity of 1 / KP. The spring 3 is fixed to the main body 8 which is one of the controlled objects. It is assumed that the sliding part 1 bears the original mass of the main body 8. Therefore, in the present invention, it is assumed that the mass of the body 8 is zero. The parameter for controlling the sliding portion 1 is the target displacement Xd, and the parameter for controlling the main body 8 is the target force Fd.

An auxiliary spring 5 of rigidity K and an auxiliary dashpot 6 of viscosity D are fixed to the sliding portion 1 at one end and to the work 9 as the work object at the other end, and are arranged in parallel. ing. The burr 10 is a part of the work 9, and is a part that is removed by the blade of the tip of the rotary tool fixed to the sliding part 1 moving in the direction perpendicular to the plane of the drawing at the same time as the sliding direction. The work 9 is deformed by removing the burr 10. It is assumed that the main body 8, the work 9 and the burr 10 constitute a system. The mechanical elements of the spring, dashpot, and mass shown in the figure schematically represent the operation, and can be realized by software in an actual system.

The target displacement Xd is the displacement that the sliding portion 1 should move. The displacement X is the displacement in which the sliding portion 1 actually exists. The target speed Vd is the speed of the sliding portion 1 for the sliding portion 1 to obtain the target displacement Xd, and the speed V is the actual speed of the sliding portion 1. The mechanical equilibrium point of the auxiliary spring 5 is the displacement X. At this time, when the target displacement Xd is given to the sliding portion 1, the restoring force f is given by the mathematical model 1 of the contact process. Restoration force f
Is partially differentiated by the difference between the displacement x and the target displacement xd, which is the rigidity K of the auxiliary spring 5, which is the amount of decrease in the rigidity of the sliding portion 1 viewed from the work 9. The partial difference of the restoring force f by the difference between the actual speed V and the target speed Vd is the auxiliary dashpot 6
Viscosity D, which is the amount of decrease in the viscosity of the sliding portion 1 when viewed from the work 9. In addition, f1 which is the first term of Formula 1 is a force required for actual deformation, and f2 which is the second term of Formula 1 is a force required for target deformation. The mathematical formula showing the process of obtaining f1 and f2 shown in Formula 1 is a mathematical model that approximates the deformation process to a known mechanical impedance model.

[0014]

[Formula 1] f = f1−f2 where f1 = K · X + D · V f2 = K · Xd + D · Vd

The target force Fd is the sliding portion 1 and the dashpot 2
This is the force received from the main body 8 by the series system composed of the spring 3 and the spring 3.
The force F is a force applied to the work 9 by the sliding portion 1. A target force Fd, a restoring force f, and a force of magnitude −F, which is a reaction force of the force F, act on the series system. The resultant force of the target force Fd, the restoring force f, and the force of magnitude −F, which is the reaction force of the force F, is defined as the resultant force ΔF. The relationship among the target force Fd, the restoring force f, the force F, and the resultant force ΔF is shown in Equation 2.

[0016]

## EQU2 ## ΔF = Fd + f−F The acceleration of the sliding portion 1 for the sliding portion 1 to obtain the target speed Vd is the target acceleration Ad. Sliding part 1 and dashpot 2
The mathematical model of the mechanical impedance, which is the equation of motion for the series system including the spring 3 and the spring 3, is expressed by Equation 3 using known general mechanics. (D / dt) is a differential operator, · is a multiplication operator, and / is a division operator. Equation 3 can also be expressed as Equation 4 by integrating both sides. ∫ is an integral operator. Equations 3 and 4 are equivalent as a mechanical impedance model.

[Formula 3] ΔF + Cd · KP · (d / dt) · ΔF = (Ad
/ KI) + Cd ・ Vd

[Equation 4] ∫ΔF ・ dt + Cd ・ KP ・ ΔF = (Vd / KI)
+ Cd ・ Xd

The target acceleration Ad can be obtained as shown in Expression 5 by using Expression 3. Further, the target velocity Vd can be obtained as shown in the equation 6 by using the equation 4. Since the expressions 3 and 4 are equivalent, the expressions 5 and 6 are also equivalent. Expression 6 is a mathematical model of the main control system in the present invention.

[Equation 5] Ad = KI · {ΔF + Cd · KP · (d / dt) ·
ΔF-Cd ・ Vd}

[Equation 6] Vd = KI · (∫ΔF · dt + Cd · KP · ΔF−
Cd ・ Xd)

Next, the impedance control method of the present invention will be described with reference to a state variable diagram. FIG. 1 is a state variable diagram showing the present invention, and shows a feedback control system for obtaining a target value which is an input required for driving when driving the system 7. However, in the figure, for the parameters indicated by the numbers and symbols in FIG. 2 and those indicated by the same numbers and symbols, the physical quantity possessed by the mechanical element indicated by the number and the physical quantity indicated by the symbol are equivalent. is there. That is, among the mechanical elements shown in FIG. 2, those which are internally configured by the control device are added with "virtual" in the prefix.

The integral gain 1 is a parameter of size KI and is the reciprocal of the virtual mass of the sliding portion of the system 7. The virtual viscosity 2 is a parameter of the magnitude Cd. The proportional gain 3 is a parameter of size Kp. The integrator 4 is a known integrator. The virtual spring 5 is a parameter of the size K, and is a force received by the work target from the control target per unit deformation amount when the control target and the work target are in contact with each other and the work target is deformed. Are equivalent. The virtual viscosity 6 is a parameter of the size D, and the force received by the work target from the control target per unit deformation speed when the control target and the work target are in contact with each other and the work target is deformed. Is equivalent to The system 7 is a system including a control target and a work target, detects a force applied to the work target by the control target, and the position and speed of the control target with respect to the work target, and determines the target of the control target with respect to the work target. It is a system that enables control of the position and the speed by inputting the position and the target speed.

The target force Fd is a parameter indicating the force for the work object to deform and the control object to contact the desired deformation surface of the work object in accordance with the strain of the work object. Is a parameter of the force to be applied to the work object. The target velocity Vd is a velocity solution of the mechanical impedance model, and is a velocity parameter that the sliding portion of the system 7 should obtain. The target displacement Xd is a solution of the displacement of the mechanical impedance model, and is a parameter of the displacement that the sliding part of the system 7 should obtain. The speed V is a parameter of the actual speed of the controlled object. The displacement X is a parameter of the actual displacement of the controlled object. The force F is a parameter of the external force that the work object receives from the controlled object. And the virtual mass,
The parameters of virtual viscosity and virtual spring are based on the relationship between the process of the tool to machine the work, the movement of the tool with respect to the work, the external force applied from the tool to the work, and the machining state that occurs on the work as a result of these movements and external forces. It can be identified in advance. That is, by setting these parameters in accordance with the work target, it is possible to absorb the distortion with respect to the drawing dimension within a certain range and deburr the set width.

FIG. 1A shows the displacement X in the system 7.
FIG. 6 is a state variable diagram showing the present invention when the position X can be controlled by detecting the velocity V and the force F, and inputting the target displacement Xd.

FIG. 1B shows the displacement X in the system 7.
FIG. 3 is a state variable diagram showing the present invention when the velocity V can be controlled by detecting the velocity V and the force F, and inputting the target velocity Vd.

FIG. 1C shows the displacement X in the system 7.
FIG. 7 is a state variable diagram showing the present invention when the displacement X can be controlled by detecting the force F and the force F and inputting the target displacement Xd. Assuming that the system is constituted by the main body 8, the work 9 and the burr 10 in FIG. 2, the system is equivalent to the system 7 in FIG. The present invention detects the displacement X and the force F in the system 7,
This is applicable even when the speed V can be controlled by inputting the target speed Vd. Furthermore, the present invention is applicable even in the system 7 when the speed V and the force F are detected and the speed V can be controlled by inputting the target speed Vd.

[0024]

According to the present invention, force feedback from a force sensor or a load cell, a mathematical model of the mechanical impedance, and an arbitrary force applied to a work object such as a work by a control object such as a processing machine The acceleration to be obtained by the controlled object is obtained, and the velocity and the position to be obtained by the controlled object are obtained from the acceleration, and the velocity control or the position control is performed to obtain the distortion of the work object with respect to the drawing dimension due to the force applied to the work object. The position feedback from the position detector or the velocity feedback from the velocity detector and the force required for the desired deformation from the mathematical model of the deformation process, and the velocity, position and deformation to be obtained by the controlled object. Obtaining the force causing the deformation from the process, the difference between the force necessary for the deformation and the force causing the deformation,
From the difference between the speed to be obtained by the controlled object and the speed by the speed detector, and the difference between the position to be obtained by the controlled object and the position by the position detector, the relative rigidity and viscosity of the controlled object and the work object are related. Obtaining a certain contact model, the contact based on the mechanical impedance and the contact model is controlled to compensate for the finish of the work target due to the rigidity and viscosity of the control target viewed from the work target, and the control target is the work target. By simultaneously compensating for the deformation of the work target due to the force applied to the work target, the finish of the work target due to the rigidity and viscosity of the control target viewed from the work target and the work target due to the force applied by the control target to the work target It is possible to adapt to the distortion with respect to the drawing size and to simultaneously compensate the deformation of the work object due to the force applied by the control object to the work object.

[Brief description of drawings]

FIG. 1 is a state variable diagram showing an embodiment of the present invention.

FIG. 2 is a one-dimensional mechanical model for explaining the present invention.

[Explanation of symbols]

1 Integral gain, or sliding part of mass equivalent to the reciprocal of the integral gain 2 Virtual viscosity, or dashpot of viscosity corresponding to the virtual viscosity 3 Proportional gain, or stiffness spring corresponding to the reciprocal of the proportional gain 4 Integrator 5 Virtual spring, or auxiliary spring having rigidity equivalent to the virtual spring 6 Virtual viscosity or auxiliary dashpot having viscosity equivalent to the virtual viscosity 7 System 8 System body 9 Workpiece 10 Burr

Claims (1)

[Claims] 1. A force applied by a controlled object to a work object, a position and a speed of the controlled object with respect to the work object are detected, and a target position and a target speed of the controlled object with respect to the work object are input to obtain the position. And a system capable of controlling the speed, the control target specifies a parameter related to the mechanical impedance so that the control target has a specified mechanical impedance, and a parameter related to the specified mechanical impedance, a detected force, and a target. Solving the equation of motion in the coordinate system of the controlled object, including the force to be corrected and the force to be corrected, to obtain the target position and the target velocity of the controlled object with respect to the work object that satisfy the equation of motion, and the target position and the target By inputting the speed into the system and controlling the position and speed, the force applied by the control target to the work target becomes the target force. Constituting the main control system for urging force control,
Further, the model of the contact process between the control target and the work target and the deformation process of the work target are configured as a mechanical impedance model in which the position and speed of the control target with respect to the work target are related to the balance, and the deformation is performed. The parameters of the mechanical impedance model for executing the contact process are set so that the process proceeds as specified, and the specified parameters, the position and speed of the controlled object with respect to the work object, the target position and the target speed are set. Is input to the mechanical impedance model, the force to be corrected is obtained as an output, the force to be corrected is input to the main control system, and the system is controlled so that the deformation process of the work object proceeds as specified. Characteristic impedance control method.