JP5130573B2 - Robot hand device - Google Patents

Description

  The present invention relates to a robot hand apparatus having fingers that flex and extend through a plurality of joints.

  This type of robot hand apparatus grips a gripping object by bending a finger so that the fingertip portion comes into contact with the gripping object. At this time, if an excessive force is applied to the gripping object or the gripping force is too small, the gripping object cannot be gripped satisfactorily. Thus, a force sensor that detects a force acting on the fingertip portion is provided on the fingertip portion, and the fingertip portion is covered with a flexible skin to increase the contact area and the friction coefficient (for example, Patent Document 1). reference). Thereby, the fingertip force with respect to the object to be grasped can be suitably controlled based on the detection of the force sensor, and the object to be grasped can be grasped stably and reliably.

  Further, by using a multi-axis force sensor such as a 6-axis force sensor as a force sensor provided at the fingertip part, it is possible to control the fingertip force with high accuracy. Here, the six-axis force sensor will be described as an example of the force sensor. The six-axis force sensor has a mechanism that can receive each of the six-axis forces in a distributed manner, and has three axes (x Axis, y-axis, z-axis) direction translation force and moment around each axis are measured. In addition, the six-axis force sensor includes a plurality of strained portions having different sensitivities with respect to force components, and the maximum measurable force value (rated measurement value) is different for each axis. Generally, the rated measurement value for the translational force in the three-axis directions is larger than the rated measurement value for the moment around each axis. Furthermore, when the rated measurement values for the translational forces in the three axis directions are compared, the rated measurement value for the z axis extending in the vertical direction with respect to the x axis and the y axis is the largest. Usually, the axis with the largest rated measurement value is the main axis, so in the six-axis force sensor, the z axis is the main axis. Even in a multi-axis force sensor other than the six-axis force sensor, the axis having the largest rated measurement value is set as the main axis.

  Further, this type of force sensor has both end surfaces as attachment surfaces, and the main shaft is located at the center of both attachment surfaces. For this reason, when the force sensor is attached to the fingertip portion of the robot hand device, the force sensor is attached to the base end of the fingertip portion so that the extension axis of the main shaft of the force sensor extends along the longitudinal direction of the finger.

However, in this type of robot hand device, the force acting on the fingertip when gripping the object to be grasped is less of the component received from the tip of the fingertip than from the tip of the fingertip. Is often larger. Therefore, when the force sensor is mounted in such a posture that the extension axis of the main shaft extends along the longitudinal direction of the finger, the force sensor receives a large force from the direction in which the rated measurement value is smaller than the main shaft direction. Thus, when this force acts on the fingertip exceeding the rated measurement value, the fingertip force cannot be controlled with high accuracy. In order to avoid this, a force sensor having a large rated measurement value may be used. However, a force sensor having a large rated measurement value has a large outer diameter and overall length (length in the main shaft direction). And when the force sensor is attached to the base end of the fingertip part so that its main axis is along the longitudinal direction of the finger, the outer diameter of the fingertip part increases corresponding to the outer diameter of the force sensor, and the fingertip can be made thinner. In addition, since the entire length of the fingertip part becomes unnecessarily long due to the influence of the total length of the force sensor, a delicate gripping operation cannot be obtained.
JP 2005-88096 A

  In view of the above points, the present invention can control the fingertip force with high accuracy using a force sensor having a relatively small rated measurement value, and can also delicately grip the fingertip portion with a small outer diameter and length. It is an object of the present invention to provide a robot hand device that can operate.

In order to achieve such an object, the present invention provides a robot hand apparatus that includes a finger that bends and stretches through a joint, includes a force sensor that detects a force acting on the fingertip, and performs a gripping operation by bending the finger. The force sensor includes an end face facing the fingertip side, an end face facing the joint side, and a main shaft having an axis positioned on the center line of both end surfaces, and the main shaft is adjacent to the tip of the fingertip portion and the joint. It is attached between the fingertip part and the joint in a posture inclined so as to face the abdomen of the fingertip formed between the base end of the part, and the extension axis of the main axis of the force sensor extends in the longitudinal direction of the finger and extends to the fingertip Extending between the first straight line passing through the tip of the part and a second straight line extending perpendicularly to the first straight line and extending toward the bending direction of the finger at the base end of the fingertip part, toward the fingertip abdomen. Features.

  According to the present invention, the force sensor is attached to the base end of the fingertip portion in an inclined posture, and the extension axis of the main shaft of the force sensor has a relatively large component of force acting on the fingertip portion when the object to be grasped is gripped. Since it extends toward the fingertip abdomen, it is possible to receive a large amount of force acting on the fingertip portion in the axial direction of the main shaft where the maximum measurable force value (rated measurement value) is large. Therefore, the force acting on the fingertip portion can be detected with certainty, and the fingertip force can be controlled with high accuracy. In addition, since the force sensor is in an inclined posture, the distance between the fingertip part and the joint is reduced with respect to the entire length of the force sensor (the dimension between the fingertip side end face and the joint side end face). It can be attached, and since the influence of the outer diameter of the force sensor on the outer diameter of the fingertip can be reduced, the outer diameter and overall length of the fingertip can be reduced, and delicate gripping operations can be performed. Can be performed.

    The force sensor employed in the present invention is effective even if it is a single-axis force sensor, but is particularly effective when the force sensor is a multi-axis force sensor such as a six-axis force sensor. For example, in a six-axis force sensor, as described above, the rated measurement value in the axial translational force of the z-axis that is the main axis is the largest. When a six-axis force sensor is employed as the force sensor in the present invention, the extension axis of the main shaft having the largest rated measurement value passes between the first straight line and the second straight line, and the fingertip abdomen. Therefore, most of the force from the fingertip abdomen that has a relatively large force component acting on the fingertip part can be received in the axial direction of the main shaft. For this reason, it is possible to avoid receiving an excessive force with respect to the x-axis and the y-axis, which are assumed to have a smaller rated measurement value than the main shaft, and a force acting on the fingertip portion without using a large rated measurement value. Can be reliably detected and the fingertip force can be controlled with high accuracy. Therefore, since the rated measurement value is relatively small and a small 6-axis force sensor can be used, the outer diameter and the total length of the fingertip portion can be easily reduced.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory side view showing a finger of the robot hand apparatus of the present embodiment, and FIG. 2 is an explanatory cross-sectional view showing a configuration of a fingertip portion.

  As shown in FIG. 1, the robot hand device of the present embodiment includes a finger 1 that bends and stretches. This robot hand device imitates a human hand and includes five fingers corresponding to a thumb, an index finger, a middle finger, a ring finger, and a little finger, but only the finger 1 corresponding to the index finger is shown in FIG. The finger is omitted. Reference numeral 2 denotes a hand part.

  As shown in FIG. 1, the finger 1 includes a terminal node portion 3, a middle node portion 4, and a base node portion 5 that are fingertip portions, and this arrangement also corresponds to a human finger. The end node portion 3 and the middle node portion 4 are connected to each other by a first joint 6 so as to be freely bent. The middle joint 4 and the base joint 5 are connected to each other by a second joint 7 so as to be bent. The proximal portion 5 is flexibly connected to the wrist portion 2 via the third joint 8. The end joint 3, the middle joint 4, and the base joint 5 are connected to each other by a link mechanism (not shown) via the joints 6, 7, and 8. When the third joint 8 is rotated, the second joint 7 and The first joint 6 is rotated in conjunction. As a result, as shown by the phantom line in FIG. 1, the end node portion 3, the middle node portion 4, and the base node portion 5 are bent toward the gripping object W to grip the gripping object W. Note that, when gripping the gripping target object W, although not shown, another finger corresponding to the mother finger is brought into contact with the gripping target object W from the side opposite to the bending finger 1. In addition, the rotation of the third joint 8 is driven by a drive source provided in the inside of the hand handle 2 or the like (not shown). For example, when the drive source is an electric motor, the output shaft of the electric motor is connected to the third joint 8. In this case, by controlling the torque of the output shaft, the force (fingertip force) with which the distal node portion 3 that is the fingertip portion of the finger 1 comes into contact with the grasped object W is controlled.

  Next, the last joint part 3 which is a fingertip part will be described. As shown in FIGS. 1 and 2, the distal node 3 is formed with a fingertip abdomen 11 between the distal end 9 and the proximal end 10. A 6-axis force sensor 12, which is a force sensor, is attached between the terminal node 3 and the first joint 6 in an inclined posture.

  As shown in FIG. 2, the terminal node 3 includes a base member 13 and a skin member 14 provided so as to cover the surface of the base member 13. The skin member 14 is made of a flexible material such as urethane, and a high friction coefficient can be obtained on the surface of the end node 3. The base member 13 is made of a hard material (synthetic resin or metal).

  As shown in FIG. 2, the six-axis force sensor 12 has a fingertip side end surface 15, which is an end surface facing the terminal node 3, is in contact with the base member 13 of the terminal node 3 and protrudes from the center of the fingertip side end surface 15. The main shaft 16 is firmly connected to the base member 13 by a screw member or the like (not shown). Further, the joint-side end surface 17 of the six-axis force sensor 12 that is an end surface facing the first joint 6 is firmly connected to a connecting member 18 connected to the first joint 6 by a screw member or the like (not shown).

  The six-axis force sensor 12 measures a six-axis force acting on the terminal node 3, that is, a translational force in the directions of three axes (x axis, y axis, z axis) orthogonal to each other and a moment around each axis. The fingertip force is controlled based on the measured value of the six-axis force output from the six-axis force sensor 12.

  Each measured value of the six-axis force in the six-axis force sensor 12 has a maximum measurable force value (rated measured value) for each axial force. Generally, the measured value of the z-axis that is the axis of the main shaft 16 is determined. The rated measurement of axial translational force is the largest. On the other hand, as indicated by the phantom line in FIG. 1, in the gripping operation with the finger 1, the stress received by the end node 3 when the end node 3 abuts the grasped object W is from the distal end 9 side of the end node 3. 2, that is, the component from the fingertip abdomen 11 side of the end node 3 rather than the component from the direction of the first straight line a extending in the longitudinal direction of the finger 1 and passing through the center of the end node 3 as shown in FIG. Is often larger.

  Therefore, as shown in FIG. 2, the six-axis force sensor 12 is attached in an inclined posture so that the main shaft 16 faces the fingertip abdomen 11 of the terminal node 3, and the extension axis z (that is, the z axis) of the main shaft 16 is , Extending toward the fingertip abdomen 11 through the first straight line a and the second straight line b extending perpendicularly to the first straight line a at the proximal end 10 of the terminal node 3 and extending toward the bending direction of the finger. Yes.

  By doing so, the 6-axis force sensor 12 can receive most of the force applied during the gripping operation by the main shaft 16 which is the z-axis having the largest rated measurement value. Even when the 6-axis force sensor 12 having a small rated measurement value is used, the force acting on the distal node portion 3 can be reliably measured. Moreover, in a general 6-axis force sensor, a sensor having a smaller rated measurement value is often smaller than a sensor having a larger rated measurement value. Therefore, the comparatively small 6-axis force sensor 12 can be used only by setting the 6-axis force sensor 12 to the inclined posture and directing the main shaft 16 toward the fingertip abdomen 11 as in the present embodiment. In addition, by setting the 6-axis force sensor 12 to the inclined posture, as shown in FIG. 1, the 6-axis force sensor 12 can be disposed at a position substantially above the first joint 6. The distance to the base end 10 of the terminal node 3 can be made small, and the total length of the terminal node 3 (the length in the direction of the first straight line a) is not unnecessarily long. Further, if the 6-axis force sensor 12 is tilted, the 6-axis force sensor 12 can be attached to the proximal end 10 of the end node 3 without being adjacent to the fingertip abdomen 11, and the 6-axis force sensor 12 can be attached to the end node. Therefore, the end node portion 3 can be formed relatively thin without being affected by the outer shape of the six-axis force sensor 12.

  In the present embodiment, only the finger 1 corresponding to the index finger has been described, but the other three fingers (not shown), that is, the three fingers corresponding to the human middle finger, ring finger, and little finger are the same as the finger 1. It is preferable to configure.

  In this embodiment, the 6-axis force sensor 12 is adopted as the force sensor. However, the force sensor is not limited to this, and may be a 1-axis force sensor or a multi-axis force sensor whose main axis is the maximum rated measurement value. May be.

An explanatory side view showing a finger of a robot hand device of one embodiment of the present invention. Explanatory sectional drawing which shows the structure of the fingertip part in this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Finger, 3 ... End node part (fingertip part), 6 ... Joint, 9 ... Tip (tip end of fingertip part), 10 ... Base end (base end of fingertip part), 11 ... Fingertip abdomen, 12 ... 6-axis force sensor (Force sensor), 15 ... fingertip side end face (end face facing fingertip side), 17 ... joint side end face (end face facing joint side), 16 ... main axis, z ... extension axis of main axis, a ... first Straight line, b ... second straight line.

Claims (1)

In a robot hand device that includes a finger that bends and stretches through a joint, includes a force sensor that detects a force acting on the fingertip, and performs a gripping operation by bending the finger,
The force sensor includes an end face facing the fingertip side, an end face facing the joint side, and a main axis having an axis positioned on the center line of both end faces, and the main axis is adjacent to the tip of the fingertip part and the joint. It is attached between the fingertip part and the joint in a posture inclined so as to face the fingertip abdomen formed between the base end of the part,
The extension axis of the main axis of the force sensor has a first straight line that extends in the longitudinal direction of the finger and passes through the tip of the fingertip portion, and is perpendicular to the first straight line at the base end of the fingertip portion and toward the bending direction of the finger. A robot hand device that extends between a second straight line extending toward a fingertip abdomen.

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