JPH06126684A - Object holder and controll method thereof - Google Patents

Abstract

PURPOSE:To make a holding object holdable finally even in the case where hardness in the holding object remains unknown, by converting a signal out of a control computer into electric power capable of driving a robot arm, and using a driving part, transmitting this converted signal to the robot arm as a constituent element. CONSTITUTION:In this object holder, a robot hand 1 is controlled either of a position control system or a force control system according to the extent of hardness in the holding object. In addition, when object holding is judged to be incompleteness from a signal out of a contact sensor 6 as well as when there is a failure in the holding, a control desired value is reset by a control computer 4, and a relative position and an attitude to the robot hand 1 is measured by a visual sensor 11. In succession, after the robot hand 1 is shifted to a position where the holding object is holdable again, a process of the object holding is executed again, and finallypositive object holding is achieved by the position control system or force control system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object gripping device using a robot hand and a control method thereof.

[0002]

2. Description of the Related Art For example, FIG. 5 shows a conventional robot hand 1.
FIG. 6 is a control block diagram in the case where an object is gripped by force control in the object gripping device according to FIG. The components involved in control are as follows. This object gripping device calculates a command value for moving the robot hand 1 from a preset reaction force target value and a reaction force actually received by the robot hand 1 fetched from the sensor signal processing unit 3. Control computer 4, a drive unit 5 for converting a command value into electric power enough to drive the robot hand 1, a robot hand 1 for gripping an object, and a reaction force received when the robot hand 1 grips an object. Force sensor 9 and a sensor signal processing unit 3 that converts a signal from the force sensor 9 into a signal that can be taken into the control computer 4.

The above-mentioned conventional object gripping device using the robot hand 1 operates as follows. That is, the control computer 4 calculates a command value such that the reaction force received by the robot hand 1 from the gripping target becomes a preset control target value, and transmits the command value to the drive unit 5. This command value is power-amplified through the drive unit 5, and the robot hand 1 is driven accordingly. The reaction force received by the robot hand 1 from the grasped object is detected by the force sensor 9 and sent to the control computer 4 through the sensor signal processing unit 3. By the feedback control loop as described above, the reaction force received by the robot hand 1 is finally set to the control target value, and the object gripping is achieved.

[0004]

The conventional object gripping device using the robot hand 1 is constructed on the premise that the hardness of the object to be gripped is known as described above. Therefore, when gripping an object of unknown hardness, it is not always possible to adopt a control method that is adapted to the hardness of the gripping target, and information on the gripping state of the gripping target (deformation amount of gripping target, gripping target The reaction force received from the robot, the contact state with the object to be grasped, etc.) is not fed back in the direction to modify the control target value, so the grasping method or the grasp control target value is autonomously applied according to the hardness of the grasped object. However, there is a problem in that it is difficult to hold them.

The object of the present invention is to grasp the object to be grasped without destroying it by autonomously changing the grasping control method or the control target value depending on the hardness of the object to be grasped, even if the hardness of the object is unknown. If it is determined that the gripping target is not gripped completely, the control target value is changed,
Release the object to be grasped once, measure the relative position and orientation of the object to be grasped with the robot hand using the visual sensor, move the robot hand to the position where the robot hand can grasp the object to be grasped again, and then try to repeatedly grasp the object. Similarly, when the gripping fails, the control target value is changed, the relative position and the posture of the gripping target with respect to the robot hand are measured by the visual sensor, and the robot arm
A gripping method in which the gripping target can be finally gripped completely in any case by moving the robot hand to a position where the gripping target can be gripped again and then repeatedly gripping, and this method is realized. To provide a device for.

[0006]

According to the present invention, the robot hand 1 is provided with a contact sensor 6 for detecting contact with an object, and a gripping interval for the object during contact with the object and during the gripping process. The position sensor 8 provided and three force sensors 9 for measuring the reaction force received from the object to be grasped are mounted, and the control computer 4 generates a hand drive output signal from these sensor signals, and whether or not object grasping has been achieved. The device is configured so that it can be determined by the output of each sensor to achieve reliable gripping.

In order to grasp an object to be grasped whose hardness is unknown, the contact with the object to be grasped is judged by the reaction of the contact sensor 6, and at the same time, the length of the object to be grasped in the grasping direction is measured by the position sensor 8. Then, the value is stored in the control computer 4 as the control initial value. In the gripping process after the contact with the grip target, the control computer 4 calculates the grip target deformation amount, that is,
The position sensor 8 has two control targets, that is, a deformation target rate related to the length of the gripping target object in the gripping direction and a reaction force target value received by the target object gripping structure 10 of the robot hand 1 from the gripping target object. While monitoring both the signal and the signal of the force sensor 9, control is performed until one of them is achieved. In this way, the position control and the force control are simultaneously performed, and finally the gripping is performed by the control method adapted to the gripping target.

When it is determined that either one of the deformation target rate of the grasped object or the reaction force target value received by the object grasping structure 10 is set to the control target value, the robot hand 1 is slightly moved vertically upward. When the displacement of the grasped object is detected, the control target value is changed and the grasped object is once released. , Visual sensor 11
The relative distance and the posture of the gripping target with respect to the robot hand 1 are measured by the robot arm 1, and the robot arm 1 moves the robot hand 1 to a position where the gripping target can be gripped again, and then the gripping is tried again. Fall)
If it is detected, the control target value is corrected and the visual sensor 1
1 is used to measure the relative position and orientation of the grasped object with respect to the robot hand 1, and after the robot arm 2 moves the robot hand 1 to a position where the grasped object can be grasped again, a retry function is provided so that the object grasping is tried again. .

In order to configure the robot hand 1 that is highly adaptable to gripping an object,
3 types of sensors (contact sensor 6, position sensor 8 and force sensor 9) are grasped by the object grasping part structure. Both the contact sensor 6 and the force sensor 9 can grasp the center of the object and grasp the object. Are mounted so that the position sensor 8 does not interfere with them.

[0010]

In the present invention, the robot hand 1 is controlled by either the position control system or the force control system according to the hardness of the object to be gripped, and grips the object. Further, when it is determined from the signal of the contact sensor 6 that the object gripping is incomplete or the gripping fails, the control target value is reset by the control computer 4, and the visual sensor 11 sets the object to be gripped on the robot hand 1. After measuring the relative position and posture, the robot arm 2 moves the robot hand 1 to a position where the object to be gripped can be gripped again, and then the object gripping process is executed again, and finally the position control system or force control system ensures Achieves excellent object gripping.

[0011]

【Example】

Example 1. FIG. 1 is a block diagram of the entire apparatus. 1 to 11 are as shown in the description of the drawing. The gripping of the object is started after the driving unit 5, the control computer 4, and the sensor signal processing unit 3 are powered on and a command for starting the object gripping is input to the control computer 4. First, the visual sensor 11 measures the relative position and orientation of the grasped object with respect to the robot hand 1, and based on this information, the robot arm 2 moves the robot hand 1 to a position where the grasped object can be grasped, and finally the robot Control is automatically performed according to the operation sequence of FIG. 3 until the hand 1 grips the gripping target.

FIG. 2 shows a method of mounting the three types of sensors (contact sensor 6, position sensor 8 and force sensor 9) mounted on the robot hand 1. An ultra-sensitive pressure sensor is used as the contact sensor 6. This sensor is the contact sensor lever 7
It is made to contact the object to be grasped indirectly via the. This is because the load resistance of the contact sensor 6 is restricted and the contact sensor 6 is waterproof. The detection of contact is determined by capturing the load change caused by the contact between the object to be grasped and the contact sensor lever 7. A transducer is used as the position sensor 8. Since the voltage output from the transducer changes according to the distance between the object gripping part structures, the gripping interval can be known. A high-sensitivity strain gauge is used for the force sensor 9. One of the three force sensors 9 is attached to a portion behind the contact sensor lever 7, and is installed so as to capture the force applied to the center of the object to be grasped. The strain gauge deforms due to the force received from the grasped object, so that the resistance value changes, and the reaction force can be known by detecting this as a voltage change. The signals from these three types of sensors are all sent to the sensor signal processing unit 3 and converted so that the control computer 4 can process them.

FIG. 3 shows an operation sequence up to the grasping of an object to be grasped whose hardness is unknown. First, the visual sensor 1
1 measures the relative position and orientation of the grasped object with respect to the robot hand 1 (initial position and orientation measurement of grasped object 1
2) Based on this information, the robot hand 1 is moved to a position where the robot arm 2 can grasp the object to be grasped. This corresponds to the initial position setting 13 of the robot hand. Next, issue an object gripping command from the control computer 4,
Start gripping the object. During this time, the object gripping part structure of the robot hand 1 approaches the object at a constant speed. When the object gripping structure contacts the object to be gripped 14, the contact sensor 6 detects this. The contact sensors 6 are on both sides of the object gripping part structure 10. When both contact sensors 6 detect contact with the object to be gripped, the value of the position sensor 8 at that time is taken as the length in the gripping direction of the object to be gripped. Remember. Next, the position control and force control 15 is entered. Through this process, the robot hand is controlled by the two control systems. One is position control that targets the deformation rate of the grasped object. This is the deformation rate with respect to the length of the object to be gripped in the gripping direction. The other is force control in which a control target is a reaction force target value received by the object gripping body structure 10 of the robot hand 1 from the gripping target. The control computer 4
Until either one of these two controls settles,
The robot hand 1 is controlled while constantly comparing the values of the position sensor 8 and the force sensor 9 with the respective control target values. The following is a brief description of an example of dividing the control modes. For example, when the object to be grasped is a soft object such as tofu, it is controlled by the deformation target rate by position control, and if it is a hard object such as a bearing ball, almost no deformation occurs. Controlled to the target value.

When it is judged that the gripping is achieved 20 by the position control or the gripping is achieved 16 by the force control, the robot arm 2 slightly lifts the object to be grasped 17 vertically upward, and at that time, the output of the contact sensor 6 causes the gripping failure 18 If the robot sensor 1 detects, the robot hand 1 is opened 22, the visual sensor 11
Then, the relative position and orientation of the grasped object with respect to the robot hand 1 are measured again, and based on this information, the robot hand 1 is moved to a position where the grasped object can be grasped again by the robot arm 2, and an attempt is made to grasp the object again. The correction of the control target value is performed by increasing the target value 21 of the position control when it is determined that the gripping can be achieved by the position control achievement 20, and by increasing the target value of the force control 19 when it is determined that the gripping can be achieved by the force control achievement 16. Deal with that. The increment of the target value in each control is defined in advance and stored in the control computer. While correcting the control target value as described above,
This control is repeated until gripping is finally achieved 23.

FIG. 4 is a control block diagram for grasping an object according to the present invention. It is shown that two feedback controls are performed in parallel, that is, position control targeting the target deformation ratio of the grasped object and force control targeting the reaction force target value. Further, by feeding back the signal from the sensor signal processing unit 3 to the control computer 4, it is judged whether or not the gripping has been achieved reliably, and if the gripping is incomplete or failed, the signal from the visual sensor 11 is sent. The robot hand 1 calculates the relative position and orientation of the gripping target with respect to the robot hand, and issues a command to the robot arm 2 to move the robot hand 1 to a position where the gripping target can be gripped again. After confirming that the object has been moved to a position where it can be gripped again, the target deformation rate setting 24 or the reaction force target value setting 25 is performed again, and the position control and the force control are performed again.

Embodiment 2.4 Of the four types of sensors, the position sensor 8 is a distance measuring sensor using light or a laser instead of a transducer, or the robot hand 1.
The same function can be realized by attaching an encoder to the built-in motor.

[0017]

The present invention is effective when the hardness of the object to be grasped is unknown, or when there are a plurality of objects to be grasped and the hardness thereof is extremely uneven. In particular, when grasping an object in an extreme environment such as another celestial body (moon, Mars, etc.), the object must be grasped under the condition that there is almost no hardness information about the grasped object. It is considered that the grip suitable for an object can be performed.

On the contrary, there is an effect that the physical information of the object can be obtained by the control information. That is, by knowing what kind of control process has been performed to grip the object, the criterion for the hardness of the object can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an object gripping device according to a first embodiment of the present invention.

FIG. 2 is a layout diagram of three types of sensors mounted on the robot hand 1 according to the first embodiment of the present invention.

FIG. 3 is an operation sequence up to object grasping according to the first embodiment of the present invention.

FIG. 4 is a control block diagram of the object gripping device according to the first embodiment of the present invention.

FIG. 5 is a control block diagram of a conventional object gripping device by force control.

[Explanation of symbols]

 1 Robot Hand 2 Robot Arm 3 Sensor Signal Processing Unit 4 Control Calculator 5 Drive Unit 6 Contact Sensor 7 Contact Sensor Lever 8 Position Sensor 9 Force Sensor 10 Object Grasping Structure 11 Visual Sensor

Claims (3)

[Claims] 1. A at least two contact sensor capable of determining a contact state with a grasped object, a position sensor capable of measuring a grasping interval of the grasped object, and a reaction force received from the grasped object at the time of grasping. A set of an object gripping part structure including at least two force sensors, a robot hand including a drive mechanism and a motor for linearly moving the object gripping part structure, a gripping target object and a robot hand. A visual sensor for measuring the relative position and orientation of the vehicle, and the four types of sensors (contact sensor, position sensor, force sensor,
A signal from a visual sensor) is converted into a signal that can be processed by a computer, and a sensor signal processing unit that sends the signal to the computer and a signal regarding the object gripping state from the sensor signal processing unit are received, and the object gripping of the robot hand is performed. A control computer for generating a signal for controlling the movement of the robot hand, and a control signal from the control computer is converted into electric power enough to drive the robot hand, and the electric power is sent to a drive mechanism and a motor of the robot hand, and A drive unit for supplying electric power to various kinds of sensors (contact sensor, position sensor, force sensor, visual sensor), a robot arm for connecting to the robot hand and moving the robot hand, and a motion of the robot arm. The control computer that generates a signal for controlling and the signal from the control computer can drive the robot arm. Is converted to electric power, the object gripping device as a constituent element and said driving unit for sending it to the robot arm. 2. A visual sensor measures the relative position and orientation of the grasped object with respect to the robot hand, and the robot arm moves the robot hand to a position where it can grasp the grasped object, and the robot hand grasps the grasped object. The contact sensor determines the contact with the object to be grasped by the reaction of the contact sensor.At the same time, the length of the object to be grasped in the grasping direction is measured by the position sensor, and the value is stored in the control computer as the control initial value. Then, the control computer, in the gripping process after the contact with the gripping target object, the deformation amount of the gripping target object, that is, the deformation target rate regarding the measured length of the gripping target object in the gripping direction, and the gripping target object from the robot. It has two control targets, the reaction force target ratio received by the object gripping part structure of the hand, while monitoring both the position sensor signal and the force sensor signal, The object gripping according to claim 1, further comprising a process of performing control until one of them is achieved, and the position control system and the force control system are autonomously selected by a gripping target object. Device control method. 3. It is judged that the robot hand can be grasped vertically when either one of the deformation target rate of the grasped object or the reaction force target value received by the object grasping structure is set to the control target value, and the robot hand is moved vertically upward. It moves slightly, and it is judged from the output of the contact sensor whether or not the gripping target is completely gripped.If the gripping condition is incomplete, the control target value is corrected and gripping is stopped. Then, the visual sensor again measures the relative position and orientation of the gripping target with respect to the robot hand, the robot arm moves the robot hand again to a position where the gripping target can be gripped, and gripping failure (falling of the gripping target) is detected. In the same manner, the visual sensor again measures the relative position and orientation of the grasped object with respect to the robot hand, corrects the control target value, and uses the robot arm to move the robot. The control method of the object gripping apparatus according to claim 1, further comprising a retry function of performing the object gripping process again after moving the hand to a position where the gripping target can be gripped again.