JP2007007860A - Object holding method of multijoint multi-finger hand - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of disadvantageous component force and unexpected motion such as rotation due to the component force. <P>SOLUTION: In nipping and holding an object with a plurality of robot hand fingertip parts including a force control means, a conditional expression for calculating the balancing force for nipping the object with the respective fingertip parts based upon the positions of the respective fingertip parts is predetermined, and while the object is held, the positions of the fingertip parts are detected by a position detector 44. The target value of generating the holding force is generated from the detected positions and the balancing conditional expression by a target force generating part 47. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an object gripping method for an articulated multi-fingered hand that grips an object with a hand.

  In order to perform work while holding each finger of a plurality of robot hands with an object sandwiched between them, it is necessary to operate the robot hand while controlling the holding state by the force generated by each finger of the robot hand. At this time, the force for holding the object with each robot hand is controlled by the control device with a predetermined magnitude and direction of the force.

  However, when the work is performed, an error in environmental information or interference with the outside may cause rolling or slipping between the holding object and the finger of the robot hand, thereby shifting the position of the finger of the robot hand.

  Further, in order to change the holding state, the position where the object is supported by the tip of the finger may be shifted. At this time, there is a problem that the balance of the force between the fingers collapses due to the position shift, and a resultant force that should not be generated is generated, or an unexpected motion such as rotation is generated by this resultant force.

  The problem to be solved by the present invention is to prevent an undesired resultant force or an unexpected movement such as rotation from being caused by this resultant force.

  The means for solving the above-described problem is that when holding the object between the finger tips of a plurality of robot hands provided with force control means, the force at which each finger tip is balanced across the object is positioned at the position of the finger tip. A conditional expression to be calculated based on the above is determined in advance, while the object is held, the position of the tip of the finger is detected, and a target value for generating a gripping force is generated from the detected position and the balance conditional expression. . The tip of a plurality of manipulators is regarded as the tip of a multi-joint multi-fingered hand, and the target value for generating a gripping force can be generated by applying the object gripping method of the multi-joint multi-fingered hand.

  By the above means, force control is performed so as to satisfy the force balance condition according to the position of the tip of each finger that generates force, so even if an unexpected shift occurs in the position of the finger tip. The balance is maintained and the operation can be continued stably.

  According to the means of the present invention, the balance force is controlled to be generated as the gripping force in accordance with the change in the position of the fingertip of the robot hand or each finger of the hand. This resultant force can prevent unexpected movement such as rotation.

FIG. 1 is a block diagram of an embodiment of the present invention. The multi-fingered robot hand 41 includes a position detection unit 44 such as an encoder, a force detection unit 42 such as a force sensor provided on the fingertip, and a joint drive unit 43. Control calculation unit 45, while feeding back the joint displacement θ and the fingertip force F obtained from the position detector 44 and the force detection unit 42, based on the target position X _d and the fingertip target force F _d of each finger, the finger joints Is calculated and output to the joint drive unit 43. The target position generation unit 46 generates and outputs a target position X _{d in} order to command the movement of the robot hand 41. The target force generation unit 47 outputs a target force F _{d in} order to command the force generated by each fingertip of the robot hand 41. Here, the target force generation unit 47 includes a gripping force command unit 48, a target force generation calculation unit 49, and a balance condition calculation unit 50. The multi-fingered hand holds each object with each fingertip interposed therebetween. Next, the target force is generated by the following method. The gripping force command unit 48 commands the balance condition calculation formula to the gripping force magnitude f and the balance condition calculation unit 50. When they are given, the target force generation operation unit 49, from the magnitude f of the position X and the gripping force of each finger, according to the conditional arithmetic expression to calculate the target force F _d, is outputted to the control arithmetic unit 45 . X used here is an actual fingertip position calculated from the joint displacement θ in the control calculation unit 45.

  FIG. 2 is an explanatory diagram of a balance condition commanded by a gripping force command from the gripping force command unit 48 in FIG. 1, and a rectangular parallelepiped object 54 is sandwiched between the fingertips 51, 52, and 53 of the three-finger hand. Represents the state held by. As illustrated, when the fingertip 51 faces the objects 52 and 53 and sandwiches the object 54, it is desired to generate a gripping force in the direction indicated by the arrow. In order to pinch with the gripping force f, a force f is generated at the fingertip 51, and a force is generated at the fingertips 52 and 53 so as to face and balance it. At this time, the distribution of the force generated by the fingertips 52 and 53 in order to balance the force and make the resultant force and the resultant moment zero is dependent on the positional relationship between the tip portions. In order to balance the forces, in the case of the positional relationship shown in (a) (the position of the fingertip 51 is a one-to-one distance with respect to 52 and 53), a force f / 2 is applied to the fingertips 52 and 53, respectively. Is generated.

  In the case of the positional relationship shown in FIG. 2B (the position of the fingertip 51 is 2 to 1 distance from the fingertips 52 and 53), a force of f / 3 is applied to the fingertip 52 and 2f / 3 is applied to the fingertip 53. generate. These force distributions can be calculated by detecting each fingertip position.

  The method of balancing the force shown in FIG. 2 is an example, and there are various ways to determine the direction of the force depending on the object and the situation, but in order to generate a balancing force at each fingertip, it depends on the positional relationship of the tip. The need to distribute power is similar. The gripping force command from the gripping force command unit 48 commands the balance condition between the position and the force as shown in FIG. 2 as an arithmetic expression for calculating the force to be generated from the fingertip position from each fingertip position. The force generation calculation is performed in the target force generation calculation unit 49.

It is a block diagram which shows the Example of this invention. It is explanatory drawing of the balance conditions in the Example of this invention.

Explanation of symbols

41 multi-fingered robot hand, 42 force detection unit, 43 joint drive unit, 44 position detection unit, 45 control calculation unit, 46 target position generation unit, 47 target force generation unit, 48 grip force command unit, 49 target force generation calculation unit , 50 Balance condition formula calculation unit, 51-53 Each fingertip of a multi-finger hand with three fingers, 54 Grasping object

Claims (2)

Predetermining a conditional expression for calculating the force that each finger tip balances across the object based on the position of the finger tip when holding the object between the finger tips of a plurality of robot hands provided with force control means, While holding an object, the position of the tip of the finger is detected, and a target value for generating a gripping force is generated from the detected position and a balance condition expression, and the object is gripped by an articulated multi-fingered hand Method. The multiple manipulator tips are regarded as the tips of a multi-jointed multi-fingered hand, and the object gripping method for the multi-jointed multi-fingered hand according to claim 1 is applied to generate a target value for generating a gripping force. A method for grasping an object of a multi-fingered hand.