KR101323217B1 - Grasping force control system and method for a robotic hand - Google Patents

Abstract

PURPOSE: A system and a method for controlling the clamping force of robotic hands are provided to be applied to control joints in a various method by using a torque servo, a current servo, a speed servo, and a position servo and to control the clamping of the robotic hands with the predetermined clamping force in which users desire. CONSTITUTION: A method for controlling the clamping force of robotic hands comprises the following steps: generating an initial clamping control instruction according to sizes of the inputted clamping force and clamping objects in the robotic hand; measuring the size of the clamping force and delivering the same to a control unit; extracting the size of the measured clamping force relative to the contact point direction; comparing the size of inputted target clamping force and the measured clamping force relative to the contact point direction and calculating the error of the size of the clamping force; calculating a joint torque input value to drive each joint of the robotic hand based on the calculated power control parameter; generating a clamping control instruction signal corresponding to the joint torque input value and delivering the same to a driving unit; and controlling the joint by generating the driving force driving each joint of the robotic hand in the driving unit. [Reference numerals] (110) Robot hand; (120) Driving unit; (130) Joint position sensor; (140) Grapping force measuring sensor; (150) Control unit; (160) User command input unit

Description

Gripping force control system and method of robot hand {GRASPING FORCE CONTROL SYSTEM AND METHOD FOR A ROBOTIC HAND}

The present invention relates to a gripping force control system and method of the robot hand, and more particularly, by using a force sensor to measure the gripping force of the robot hand performing the gripping operation, and by using this as feedback information to precisely grasp the gripping operation A gripping force control system and method for a robot hand that can be performed.

Recently, many joints and development of robot hands having a dodge have been made. One of the main functions of the robot hand is to grasp objects with precise force, especially when dealing with fragile objects (light bulbs, eggs, etc.) or objects that are easily deformed (paper cups, plastic cans, etc.) or with humans. This is an important feature to ensure stability in the work that the interaction takes place. However, until now, techniques for accurately controlling the gripping force of the robot hand have been insufficient.

In the conventional gripping force control method, the gripping force commanded by the controller is different from the value measured in the actual system due to characteristics such as loss of efficiency and nonlinear frictional force in the driving unit, and thus, the user cannot smoothly control the gripping force desired by the user. .

Patent Publication 10-2011-0013588 (Doosan Infracore Co., Ltd.) 2011.02.10. Patent Publication 10-2010-0066895 (Gyeongsang National University Industry-Academic Cooperation Foundation) 2010.06.18.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gripping force control system and method for an adaptive control type robot hand that uses a gripping force information measured by a force sensor as feedback information to change a gripping force parameter commanded by a controller. will be.

Another object of the present invention is to provide a gripping force control system and method for a robot hand that can be applied to various types of joint control using a torque servo, a current servo, a speed servo, a position servo, and the like.

A gripping force control system for a robot hand according to an embodiment of the present invention for achieving the above object comprises a robot hand which is composed of a plurality of robot fingers and performs a gripping operation on an object; A driving unit connected to each joint of the robot hand to transmit a driving force for operating the joint; A joint position sensor for measuring position information of each joint of the robot hand in real time and transferring the position information to the controller; A gripping force sensor attached to a part of the robot hand and measuring a force acting between the robot hand and the object at a position where the robot hand and the object come into contact with each other and transmitting the force to the controller; A user command input unit which is an interface for inputting a size of a gripping force of a robot hand desired by a user; And generate a grip control command signal by integrating the joint position information sensed by the joint position sensor and the grip force information measured by the grip force measurement sensor so as to follow the magnitude of the grip force input to the user command input unit, and transmit the generated grip control command signal to the driving unit. It includes a control unit.

In the user command input unit, information about the weight of the object to be gripped is separately input to the control unit, and the control unit adjusts the grip control by reflecting information about the weight of the object on the magnitude of the gripping force input to the user command input unit. It can generate a command signal.

The gripping force control system of the robot hand may further include a gripping signal processor for low-pass filtering the gripping force signal measured by the gripping force measuring sensor and transferring the gripping force signal to the controller.

A gripping force control method of a robot hand according to an embodiment of the present invention includes the steps of inputting a desired gripping force through a user command input unit; Generating an initial gripping control command in the control unit according to the input gripping force, and gripping an object in the robot hand; Measuring a magnitude of a gripping force acting on an object in a gripping force sensor attached to the robot hand and transmitting the magnitude of the gripping force to the controller; Extracting a magnitude of the gripping force measured by the gripping force sensor with respect to a contact point direction; Calculating an error of the gripping force level by comparing a magnitude of the target gripping force input to the user command input unit with a magnitude of the measured gripping force in the contact point direction; Calculating a force control parameter to correct the error of the gripping force magnitude; Calculating joint torque input values for driving each joint of the robot hand based on the calculated force control parameter; And generating and transmitting a grip control command signal corresponding to the joint torque input value to a driving unit, and generating a driving force for driving each joint of the robot hand by the driving unit to control the joint.

The gripping force control method of the robot hand may further include performing low-pass filtering on the gripping force signal measured by the gripping force measuring sensor and transferring the gripping force signal to the controller.

In order to calculate the joint torque input value from the force control parameter, a Jacobian matrix through static kinematics calculation may be applied.

When the joint control is a torque servo method, the controller may include a torque controller, and the controller may further include generating, by the torque controller, a grip control command signal based on the joint torque input value.

When the joint control is a current servo method, the controller includes a current controller, calculates a joint current input value by applying a current-torque conversion constant to the joint torque input value, and calculates a corresponding joint current input value in the current controller. The method may further include generating a grip control command signal based on the operation.

When the joint control is a position servo method, the controller includes a position controller, calculates a joint position input value by applying a transfer function of a joint position error with respect to the joint torque input value, and calculates a corresponding joint position in the position controller. The method may further include generating a grip control command signal based on the input value.

When the joint control is a speed servo method, the controller includes a speed controller, calculates a joint speed input value by applying a transfer function of a joint speed error with respect to the joint torque input value, and calculates a corresponding joint speed in the speed controller. The method may further include generating a grip control command signal based on the input value.

The gripping force control apparatus and method of the robot hand according to the present invention has the effect of performing the gripping control of the robot hand with a predetermined gripping force desired by the user.

In addition, the gripping force control apparatus and method of the robot hand according to the present invention, through the feedback using the force sensor, there is an effect that can precisely perform the gripping motion control of the robot hand with a large dynamic change.

In addition, the gripping force control device and method of the robot hand according to the present invention has an effect that can be applied to various types of joint control using a torque servo, a current servo, a speed servo, a position servo.

1 is a block diagram showing the configuration of a gripping force control system of a robot hand according to an embodiment of the present invention.
2 is a diagram illustrating an exemplary robot hand and gripping force sensor of the present invention.
3 is a view for explaining the grip force control of the robot hand.
4 is a flowchart illustrating a gripping force control method of a robot hand according to an exemplary embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the gripping force control system and method of the robot hand according to an embodiment of the present invention.

1 is a block diagram showing the configuration of a gripping force control system of a robot hand according to an embodiment of the present invention.

Referring to FIG. 1, the gripping force control system 100 of the robot hand of the present invention includes a robot hand 110, a driver 120, a joint position sensor 130, a gripping force sensor 140, a controller 150, and a user. Command input unit 160 is included.

The robot hand 110 is composed of a plurality of robot fingers and performs a gripping operation on an object. The robot hand 110 may be composed of a simple gripper having only one degree of freedom or a plurality of fingers having multiple degrees of freedom. 2 illustrates an example in which the robot hand 110 is configured as a gripper in a simple form.

The driver 120 is connected to each joint of the robot hand 110 to transmit a driving force for operating the joint.

The joint position sensor 130 measures the position information of each joint of the robot hand 110 in real time and transmits it to the controller 150.

The gripping force sensor 140 is attached to a part of the robot hand, and measures the force acting between the robot hand 110 and the object at a position where the robot hand 110 contacts the object. The gripping force sensor 140 may be a force sensor of one or more axes when the robot hand 110 is a one degree of freedom gripper, and may be a three axis force sensor when the robot hand 110 is a multi degree of freedom robot hand. Can be. The gripping force signal measured by the gripping force measurement sensor 140 is transmitted to the controller 150, and before the gripping force signal is transmitted to the controller 150, the gripping signal processor (not shown) performs low-pass filtering on the gripping force signal. By doing so, the purified signal value may be transmitted to the controller 150.

The user command input unit 160 is an interface for inputting the size of the gripping force desired by the user. The user may input different gripping forces according to the object to be gripped. In addition, the user command input unit 160 may separately input information about the weight of the object to be gripped and transmit it to the controller.

The controller 150 integrates the grip position information detected by the joint position sensor 130 and the grip force information measured by the grip force measurement sensor 140 to follow the magnitude of the grip force input to the user command input unit 160 to control the grip. The command signal is generated and transmitted to the driver 120. The gripping control command signal generated by the controller 150 may be updated in real time based on the feedback information transmitted from the joint position sensor 130 and the gripping force sensor 140 and transmitted to the driving unit 120. In addition, when the information regarding the weight of the object as well as the gripping force is input to the user command input unit 160, the controller 150 reflects the information about the weight of the object on the magnitude of the gripping force input to the user command input unit 160. Thus, a corrected grip control command signal can be generated.

3 is a view for explaining the grip force control of the robot hand.

Referring to FIG. 3, a robot hand having multiple degrees of freedom is illustrated, and it can be seen that the magnitude of the command force and the grip force according to the grip control command signal transmitted from the controller 150 is different. This is because the direction of command force of the robot hand moving according to the grip control command signal and the direction in which the grip force acts on the object are different. Also, even if the same command force is applied, the magnitude of the gripping force varies with the weight of the object.

Therefore, in order to generate a gripping force of a desired size, in the present invention, a command force corresponding to a gripping force of a desired size is provided through a feedback operation of transferring the gripping force information measured by the gripping force sensor 140 to the controller 150. Generates.

4 is a flowchart illustrating a gripping force control method of a robot hand according to an exemplary embodiment of the present invention.

Referring to FIG. 4, first, a user inputs a desired grip force through the user command input unit 160 (S410). At this time, if information on the weight of the object to be gripped is also input, the size of the gripping force can be configured to be modified according to the weight of the object. Subsequently, the controller 150 generates an initial gripping control command according to the input gripping force, and performs an operation of gripping an object from the robot hand 110.

Subsequently, the gripping force sensor 140 attached to the robot hand 110 measures the size of the gripping force acting on the object (S420). The gripping force signal measured by the gripping force measuring sensor 140 is transmitted to the controller 150, and the gripping force signal processing unit (not shown) performs low-pass filtering on the gripping force signal to control the refined signal value. 150).

Next, the controller 150 extracts the size of the gripping force measured by the gripping force sensor 140 with respect to the contact point direction (S430). This extracts the magnitude of the force with respect to the direction in which the command force acts in the measured vector component of the gripping force (see Figure 3).

Subsequently, the controller 150 calculates an error of the gripping force level by comparing the target gripping force input to the user command input unit 160 with the magnitude of the measured gripping force in the contact point direction (S440).

Subsequently, the controller 150 calculates a force control parameter for correcting an error of the gripping force magnitude. The force control parameter is a parameter for generating a command force applied to the robot hand 110.

Subsequently, the controller 150 calculates joint torque input values for driving each joint of the robot hand 110 based on the calculated force control parameter (S460). In order to calculate the joint torque input value from the force control parameter, a Jacobian matrix through static kinematics calculation may be applied.

Subsequently, the controller 150 generates a grip control command signal corresponding to the joint torque input value and transmits it to the driver 120, and the driver 120 generates a driving force for driving each joint of the robot hand 110. The joint is controlled (S470).

Here, when the joint control is a torque servo method, the controller 150 includes a torque controller and generates a grip control command signal based on the joint torque input value in the torque controller.

In another embodiment of the present invention, when the joint control is a current servo method, the controller 150 includes a current controller, calculates a joint current input value by applying a current-torque conversion constant to the joint torque input value, The current controller generates a grip control command signal based on the corresponding joint current input value.

In another embodiment of the present invention, when the joint control is a position servo method, the controller 150 includes a position controller, and calculates a joint position input value by applying a transfer function of joint position error to the joint torque input value. The position controller generates a grip control command signal based on the corresponding joint position input value.

In another embodiment of the present invention, when the joint control is a speed servo method, the controller 150 includes a speed controller and calculates a joint speed input value by applying a transfer function of joint speed error to the joint torque input value. The speed controller generates a grip control command signal based on the joint velocity input value.

Subsequently, when the control of the gripping operation of the robot hand 110 is to be continuously performed, each step is repeatedly executed sequentially from step S420 (S480).

Hereinafter, the joint control of the speed servo method will be described.

In general, a position or speed controller is required for force control of the robot hand 110, and an integral controller is required to zero the steady state position error.

를 발생시키기 위해 사용된다.Therefore, the force controller is in the form of a PI controller, which is the internal torque as shown in the following equation

Used to generate

는 명령 파지력이며,

는 비례 계수이고,

는 적분 계수이다. 또한,

는

과 같이 정의되는 힘 오차이고,

는 원하는 목표 파지력이고,

는 힘 센서에서 측정된 파지력이다. here,

Is the command grip power,

Is a proportional coefficient,

Is the integral coefficient. Also,

The

Is the force error defined by

Is the desired target grip power,

Is the gripping force measured by the force sensor.

는 작업 공간 힘을 관절 공간 토크로 변환하기 위한 위치 자코비안 트랜스포즈(position jacobian transpose)이다.

은 제1 핑거로부터 제2 핑거에 이르는 파지 벡터이며,

로 정의된다. 여기서,

와

는 각각 제1 핑거와 제2 핑거의 위치 벡터이다.

는 세컨드 유클리디언 놈(second Euclidean norm)이다.

Is a position jacobian transpose for converting work space force into joint space torque.

Is a phage vector from the first finger to the second finger,

. here,

Wow

Are the position vectors of the first finger and the second finger, respectively.

Is the second Euclidean norm.

는 파지 방향에서 유닛 벡터이다. Also,

Is the unit vector in the gripping direction.

는 초기의 힘 오차를 감소시키기 위해 주어지며, 적분은 정상상태 힘 오차를 감소시킨다. 따라서, 힘 제어를 통한 파지력 제어가 가능하며, 각 관절을 동작시키기 위해 토크로 변환할 필요가 있다. 이를 위해, 상기 수학식 1을 통해 내부 토크

를 산출할 수 있다.

Is given to reduce the initial force error, and the integration reduces the steady state force error. Therefore, gripping force control through force control is possible and needs to be converted into torque in order to operate each joint. To this end, the internal torque through the equation (1)

Can be calculated.

는 하기 수학식 2와 같이 나타낼 수 있다. The speed servo method has an internal speed control loop including a PI controller, and the internal torque of Equation 1

Can be expressed as in Equation 2 below.

는 원하는 목표 속도이고,

는 측정 속도이다. 또한,

는 비례 계수이고,

는 적분 계수이다. here,

Is the desired target speed,

Is the measurement speed. Also,

Is a proportional coefficient,

Is the integral coefficient.

Equation 2 is expressed as a frequency domain as follows.

In addition, since the speed PI control and the position PD control are the same, Equation 3 can be summarized as follows.

로 변환될 수 있다. 상기 수학식 4에 최종값 정리(Final value theorem)를 적용하면 다음과 같다. Calculated internal torque is input speed

Lt; / RTI > When final value theorem is applied to Equation 4, it is as follows.

는

에 의해 다음과 같이 설계된다. If the robot hand grips the object with the desired force, the robot must maintain its position to force the object. Transfer function

The

It is designed as follows.

이면,

이다. According to Equation 6,

If so,

to be.

가 하기 수학식 같이

를 생성하기 위해 제안된다. In gripping force control, a corrected command gripping force

Like the following equation

Is proposed to generate.

는 각각 비례 계수, 적분 계수, 감쇠 계수이며, 양(positive)의 정해진 값들이다. 또한,

는 파지 방향에서 작업 공간 감쇠이며,

는 파지 방향에서 측정된 힘이다. 또한,

는 힘 센서에서 측정된 힘이다. here,

Are proportional coefficients, integral coefficients, and damping coefficients, respectively, and are positive fixed values. Also,

Is the workspace attenuation in the grip direction,

Is the force measured in the holding direction. Also,

Is the force measured by the force sensor.

Therefore, the following equation holds.

는 입력 속도를 얻는데 적용된다. Calculated

Is applied to obtain the input speed.

가 포화 상태가 되면(saturate),

는 내부 힘에 대해 위치를 유지하도록 0이 된다. 한편, 만약 물체의 중력 효과가 상호작용 동안 고려되지 않으면, 파지력 제어가 적절히 수행되더라도 제어가 실패할 수 있다. 이는 중력에 의해 물체를 파지한 로봇 핸드가 하방으로 처질 수 있기 때문이다.

When is saturated,

Is zero to maintain position with respect to internal forces. On the other hand, if the gravitational effect of the object is not taken into account during the interaction, the control may fail even if the gripping force control is properly performed. This is because the robot hand holding the object by gravity may sag downwards.

와

의 합이 0이 되면, 물체의 무게로 인해 로봇 핸드가 하방으로 처진다. 처짐을 방지하기 위해, 보상 힘

가 제어기에 다음 식과 같이 추가된다. In order to consider gravity compensation, referring back to FIG. 3, the robot fingers above and below the object are named first and second fingers, respectively. Force by the first and second fingers

Wow

If the sum is zero, the weight of the object causes the robot hand to sag downwards. To prevent sag, compensatory force

Is added to the controller as

는 물체의 중력이며, 파지 방향에 반영된다. here,

Is the gravity of the object and is reflected in the gripping direction.

The present invention can also control the gripping force in consideration of the gravity compensation according to the weight of the object, it is possible to control the grip force of the robot hand more precise.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

100: gripping force control system of the robot hand
110: robot hand
120:
130: joint position sensor
140: gripping force sensor
150:
160: user command input unit

Claims (10)

delete delete delete Inputting a desired amount of gripping force through a user command input unit;
Generating an initial gripping control command in the control unit according to the input gripping force, and gripping an object in the robot hand;
Measuring a magnitude of a gripping force acting on an object in a gripping force sensor attached to the robot hand and transmitting the magnitude of the gripping force to the controller;
Extracting a magnitude of the gripping force measured by the gripping force sensor with respect to a contact point direction;
Calculating an error of the gripping force level by comparing a magnitude of the target gripping force input to the user command input unit with a magnitude of the measured gripping force in the contact point direction;
Calculating a force control parameter to correct the error of the gripping force magnitude;
Calculating joint torque input values for driving each joint of the robot hand based on the calculated force control parameter; And
Generating a grip control command signal corresponding to the joint torque input value and transmitting the generated grip control command signal to a driving unit, wherein the driving unit generates a driving force for driving each joint of the robot hand, thereby controlling the joint;
When the joint control is a torque servo method, the control unit includes a torque controller, and the torque controller further comprises generating a grip control command signal based on the joint torque input value. Gripping force control method. The gripping force of the robot hand according to claim 4, further comprising low-pass filtering the gripping force signal measured by the gripping force sensor to the control unit by low-pass filtering. Control method. 5. The method of claim 4, wherein a Jacobian matrix is applied through static kinematic calculation to calculate joint torque input from the force control parameter. delete Inputting a desired amount of gripping force through a user command input unit;
Generating an initial gripping control command in the control unit according to the input gripping force, and gripping an object in the robot hand;
Measuring a magnitude of a gripping force acting on an object in a gripping force sensor attached to the robot hand and transmitting the magnitude of the gripping force to the controller;
Extracting a magnitude of the gripping force measured by the gripping force sensor with respect to a contact point direction;
Calculating an error of the gripping force level by comparing a magnitude of the target gripping force input to the user command input unit with a magnitude of the measured gripping force in the contact point direction;
Calculating a force control parameter to correct the error of the gripping force magnitude;
Calculating joint torque input values for driving each joint of the robot hand based on the calculated force control parameter; And
Generating a grip control command signal corresponding to the joint torque input value and transmitting the generated grip control command signal to a driving unit, wherein the driving unit generates a driving force for driving each joint of the robot hand, thereby controlling the joint;
When the joint control is a current servo method, the controller includes a current controller, calculates a joint current input value by applying a current-torque conversion constant to the joint torque input value, and calculates a corresponding joint current input value in the current controller. And generating a grip control command signal based on the gripping force control method of the robot hand. Inputting a desired amount of gripping force through a user command input unit;
Generating an initial gripping control command in the control unit according to the input gripping force, and gripping an object in the robot hand;
Measuring a magnitude of a gripping force acting on an object in a gripping force sensor attached to the robot hand and transmitting the magnitude of the gripping force to the controller;
Extracting a magnitude of the gripping force measured by the gripping force sensor with respect to a contact point direction;
Calculating an error of the gripping force level by comparing a magnitude of the target gripping force input to the user command input unit with a magnitude of the measured gripping force in the contact point direction;
Calculating a force control parameter to correct the error of the gripping force magnitude;
Calculating joint torque input values for driving each joint of the robot hand based on the calculated force control parameter; And
Generating a grip control command signal corresponding to the joint torque input value and transmitting the generated grip control command signal to a driving unit, wherein the driving unit generates a driving force for driving each joint of the robot hand, thereby controlling the joint;
When the joint control is a position servo method, the control unit includes a position controller, calculates a joint position input value by applying a transfer function of joint position error with respect to the joint torque input value, and inputs a corresponding joint position in the position controller. And a step of generating a grip control command signal based on the value. Inputting a desired amount of gripping force through a user command input unit;
Generating an initial gripping control command in the control unit according to the input gripping force, and gripping an object in the robot hand;
Measuring a magnitude of a gripping force acting on an object in a gripping force sensor attached to the robot hand and transmitting the magnitude of the gripping force to the controller;
Extracting a magnitude of the gripping force measured by the gripping force sensor with respect to a contact point direction;
Calculating an error of the gripping force level by comparing a magnitude of the target gripping force input to the user command input unit with a magnitude of the measured gripping force in the contact point direction;
Calculating a force control parameter to correct the error of the gripping force magnitude;
Calculating joint torque input values for driving each joint of the robot hand based on the calculated force control parameter; And
Generating a grip control command signal corresponding to the joint torque input value and transmitting the generated grip control command signal to a driving unit, wherein the driving unit generates a driving force for driving each joint of the robot hand, thereby controlling the joint;
When the joint control is a speed servo method, the controller includes a speed controller, calculates a joint speed input value by applying a transfer function of a joint speed error with respect to the joint torque input value, and inputs a corresponding joint speed in the speed controller. And a step of generating a grip control command signal based on the value.

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