WO2010074045A1

WO2010074045A1 - Robot hand system with gripping section

Info

Publication number: WO2010074045A1
Application number: PCT/JP2009/071267
Authority: WO
Inventors: 定夫尾股; 嘉延村山
Original assignee: 学校法人日本大学
Priority date: 2008-12-26
Filing date: 2009-12-22
Publication date: 2010-07-01
Also published as: JP2010149262A

Abstract

The hardware portion of a robot hand system (10) is configured by including a lifting actuator (12), gripping actuators (14), and probes (20) each provided to the gripping end at the tip of each multi-joint section (17). A section (50) for detecting contact and the degree of slip and connected to the probes (20) has a function of discriminatorily detecting the following states: a non-contact state in which an object is not in contact with the probes (20) at all, a contact and gripping state in which the probes (20) and the object are not moving relatively, and a slip state in which the probes (20) and the object are moving relative to each other and are in what is called a slipping condition. With the use of this function, a control section (70) drives the gripping actuator (14) so that the object can be held with a minimum gripping force.

Description

Robot hand system having a gripper

The present invention relates to a robot hand system having a gripper, and more particularly to a robot hand system having a gripper that moves relative to an object and grips the object.

An articulated robot is used to move an arm on which a work tool or the like is mounted on an object to an arbitrary position. Also, a robot hand having articulated fingers is used to perform an operation such as holding an object and carrying it to an arbitrary place. A robot hand having a gripping unit needs to detect slippage between the gripping unit that is a fingertip and the target in order to grip the target firmly.

For example, Patent Document 1 discloses a method of disposing a tactile sensor including a plurality of pressure sensors on a finger surface having a flexible structure as a slip detection device for a finger surface of a robot hand and acting on a fingertip at the start of grasping a grasped object. Measuring line contact force and initial pressure barycentric position is disclosed. When the gripping object is lifted, the flexible structure is deformed according to gravity, which is an external force acting on the gripping object, so that the pressure centroid position changes. In anticipation, it is stated that the gripping force is increased when slipping occurs.

Also, as a technique related to the present invention, Patent Document 2 discloses a technique for accurately measuring the hardness of an object using ultrasonic waves. This technology includes a vibrator that injects ultrasonic waves into a substance, a vibration detection sensor that detects a reflected wave from the substance, an amplifier having an input terminal connected to a signal output terminal of the vibration detection sensor, and an output terminal of the amplifier and vibration. When there is a phase difference between the input waveform to the transducer and the output waveform from the vibration detection sensor, this is a phase that changes the frequency and shifts the phase difference to zero. The shift circuit includes a shift circuit and frequency change amount detecting means for detecting a frequency change amount for shifting the phase difference to zero. Here, in the frequency change amount detection means, the phase difference due to the difference in hardness is shifted to zero and converted into a frequency change amount. In this conversion, a reference transfer function indicating the relationship between the amplitude gain and phase of the reflected wave with respect to the frequency is obtained in advance and used.

JP 2006-297542 A Japanese Patent Laid-Open No. 9-146991

When gripping an object with a robot hand system having a gripping part, the object may be damaged if the gripping force is excessively strong. For example, when a soft object such as tofu or the like whose shape is damaged if it is gripped excessively strongly, the gripping force needs to be minimized. If the method of Patent Document 1 is used, there is a possibility of starting from a small gripping force to obtain a necessary gripping force. However, it is necessary to arrange a plurality of pressure sensors on the finger surface. The finger that is the gripping part is enlarged.

An object of the present invention is to provide a robot hand system having a grip portion that can grip an object with a minimum grip force without requiring a plurality of sensors.

The present invention is an application of the hardness measurement technique of Patent Document 2, and when a probe having a vibrator that makes an ultrasonic wave incident on a substance and a vibration detection sensor that detects a reflected wave from the substance contacts the object, This is based on the fact that there is a phase difference between the incident wave and the reflected wave as compared to before contact. That is, the hardness measurement technique of Patent Document 2 is based on the fact that the phase difference between the incident wave and the reflected wave when the probe is brought into contact with the object has a correlation with the hardness of the object. There is a phase difference between the incident wave and the reflected wave at the moment when the probe comes into contact with the object before converting to hardness. That is, the contact between the probe and the object can be detected in a state where the contact pressure is almost zero.

In the hardness measurement technique of Patent Document 2, a phase difference is converted into a frequency change using a reference transfer function. Therefore, if the converted frequency change is observed, it can be detected that contact has occurred when the frequency changes from the non-contact frequency at which the probe and the object are not in contact. Assuming that the frequency when contact is detected is the contact frequency, even if contact is made once, if the probe and the object are separated from each other, the frequency returns from the contact frequency to the non-contact frequency.

From this, it was thought that a frequency change might occur when the object slips from the probe, and when an experiment was conducted, what was the frequency at the time of contact in the contact state was detected from the probe. It was confirmed that when an object slips, its frequency changes toward the non-contact frequency. Therefore, by applying the hardness measurement technique disclosed in Patent Document 2, contact detection between the probe and the object and slip detection can be performed. In order to realize this principle, the present invention provides a robot hand system having a gripping part by configuring the following specific means.

That is, a robot hand system having a gripping part according to the present invention includes a gripping part that moves relative to an object and grips the object, and a vibrator that is provided in the gripping part and injects vibration into the object. A probe having a vibration detection sensor for detecting a reflected wave from the object, an amplifier having an input end connected to the output end of the vibration detection sensor, and between the output end of the amplifier and the input end of the vibrator If a phase difference occurs between the input waveform to the vibrator and the output waveform from the vibration detection sensor, the phase difference is shifted to zero by changing the frequency of the input vibration to the vibrator. The phase shift circuit that outputs the input frequency to the vibrator when the value becomes zero, and the frequency that the phase shift circuit outputs from the non-contact state frequency when there is no object in the gripping part, Beyond threshold frequency When the wave number changes, the contact state detection unit that detects that the grip unit is in contact with the object and gripped, and the frequency output by the phase shift circuit, from the contact grip state that exceeds the contact grip threshold frequency, When the frequency changes in the direction of the contact state frequency, the sliding state detection unit detects that the object is slipping from the gripping unit by changing from the contact gripping state, and the gripping unit is relative to the object. A control unit that controls a gripping movement that is a movement, and the control unit grips and moves the gripping unit with respect to the object in a direction in which the target object is in contact with the gripping unit from a state in which the target object is not in contact with the gripping unit. A contact state stop means for stopping the gripping movement when the state detection unit detects contact gripping between the gripping part and the object, and a target for the gripping part while detecting the gripping and stopping the gripping movement. Things are phase The direction in which the gripper returns the object from the slipping state to the contact gripping state according to the amount of change in the frequency output by the phase shift circuit when the slipping state detection unit detects the slipping state by moving in the gravitational direction. Furthermore, the apparatus further includes a slip handling means for gripping and moving the gripping part, and a grip maintaining means for stopping the gripping movement of the gripping part when the slipping state detection unit no longer detects the slipping state.

Further, in the robot hand system having the gripping part according to the present invention, the slipping state detecting part has a differentiating means for differentiating the frequency output from the phase shift circuit, and the phase shift circuit outputs based on the output of the differentiating means. It is preferable to detect slippage due to a change in frequency.

Further, in the robot hand system having the gripping part according to the present invention, it is obtained in advance based on the frequency change output by the phase shift circuit when the slipping state detecting unit stops detecting the slipping state by the processing of the gripping maintaining means. It is preferable to provide hardness output means for outputting the hardness of the object using the relationship between frequency change and hardness.

With the configuration described above, the robot hand system having the gripping unit has a configuration including the phase shift circuit described in Patent Document 2, and the frequency output by the phase shift circuit is not in a state where there is no object in the gripping unit. When the frequency changes from a contact state frequency exceeding a predetermined contact gripping threshold frequency, it is detected that the gripping part has touched and gripped the object, and from the contact gripping state exceeding the contact gripping threshold frequency When the frequency changes in the direction of the non-contact state frequency, the object is detected as a sliding state in which the object is sliding from the contact state with respect to the grip portion.

Then, the control unit that controls the gripping movement of the gripping part with respect to the target object grips and moves the gripping part relative to the target object in a direction in which the target object is not in contact with the gripping part, The gripping movement is stopped when contact gripping between the gripping part and the target object is detected, and the target object is gravity relative to the gripping part while detecting the contact gripping and stopping the relative movement. When the sliding state is detected by moving in the direction, the gripping unit further grips and moves the object in the direction to return the object from the sliding state to the contact gripping state according to the amount of change in the frequency output by the phase shift circuit. In response to slipping, when the slipping state detection unit no longer detects the slipping state, gripping maintenance is performed by stopping the relative gripping movement of the gripping part with respect to the object.

The magnitude of the contact pressure or gripping force between the probe and the object when detecting contact gripping can be determined by setting the contact gripping threshold frequency, so a small value, for example, a gripping force of several grams Depending on the case, the gripping force can be 1 gram or less. When the robot hand system lifts the target object or when the target object is a container and another object such as water is added to the target object, the target slips against the probe. The gripping force can be increased until it is no longer detected. Therefore, it is possible to grip an object with a minimum gripping force with one probe without requiring a plurality of sensors for one gripping portion.

Further, in the robot hand system having the gripping unit, the slipping state detection unit has a differentiating unit that differentiates the frequency output from the phase shift circuit, and changes in the frequency output from the phase shift circuit based on the output of the differentiating unit. Slip detection by This makes it possible to reliably detect slippage.

Also, in a robot hand system having a gripping part, a frequency change and a hardness obtained in advance are determined based on the frequency change output by the phase shift circuit when the slipping state detection part stops detecting the slipping state by the processing of the gripping maintenance means. Using the relationship, the hardness of the object is output. Thereby, it is possible to know the softness and hardness of the object being gripped.

In embodiment which concerns on this invention, it is a figure explaining the structure of the robot hand system which has a holding part. In embodiment which concerns on this invention, it is detail drawing around a probe. In embodiment which concerns on this invention, it is a block diagram explaining the structure of a contact and slip detection part. In the embodiment according to the present invention, the probe is brought into contact with the object from the non-contact state in which the probe and the object are not in contact at all, and the probe is moved up and down from that state. It is a figure explaining the mode of the state of each element when trying to lift an object. In embodiment which concerns on this invention, when slip generation | occurrence | production is detected, it is a figure which shows a mode that the number of grasping steps is changed and slip generation | occurrence | production is suppressed. 4 is a flowchart showing a procedure of the first half of processing for gripping an object with a minimum gripping force in the robot hand system according to the embodiment of the present invention. It is a flowchart which shows the procedure of the latter half part of the process following FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, a mass of silicon rubber will be described as an object, but this is moderately soft and used as an example in which the outer shape is damaged when excessive gripping force is applied. Further, biological tissues, tofu, rubber balls, etc. may be used as objects. In addition, a container or the like when a slip occurs between a gripping part and an object by adding another container to the container while it is once gripped, such as a rigid container. Also good. The materials, shapes, dimensions, numerical values, and the like described below are examples, and these contents can be appropriately changed according to the purpose of use.

In the following, as a gripping part for gripping an object, an arm driven by a lift actuator and a gripping actuator and three multi-joint parts will be described. This is a hardware model that simulates the actions of the wrist and thumb, the index finger, and the middle finger. It is an example, Comprising: Even if it is the structure of those other than this, what is necessary is just to move relatively with respect to a target object and hold | grip a target object. In the simplest configuration, the gripping unit may be configured by one movable arm that moves relative to the fixed wall and grips the object. Thus, the number of movable parts that sandwich the object may be one or more. Further, the number of joints of the movable arm that sandwiches the object is preferably two or more, and may be a multi-joint, but may be one joint depending on the case.

In the following, similar elements are denoted by the same reference symbols in all drawings, and redundant description is omitted. In the description in the text, the symbols described before are used as necessary.

FIG. 1 is a diagram illustrating the configuration of a robot hand system 10 having a gripping unit. The robot hand system 10 having a gripping unit executes a hardware part of a robot hand that can simulate the movements of the three fingers of the thumb, the index finger, and the middle finger and the wrist, and software that controls the operation of the robot hand. It consists of a control part. The control part is illustrated as a control unit 70. Hereinafter, the robot hand system 10 having the gripping portion is simply referred to as the robot hand system 10 unless otherwise specified.

The hardware part of the robot hand system 10 includes one lifting actuator 12 that simulates the wrist movement, and a plurality of gripping actuators 14 that simulate the movement of the multi-joint portion 17 of the thumb, index finger, and middle finger. And a probe 20 provided at the grip end of each tip of the multi-joint portion 17 of the thumb, index finger, and middle finger. All of these correspond to a gripping unit in a broad sense as a unit that moves relative to the object and grips the object.

The elevating actuator 12 rotates two sets of arms 13 that are rotatable around a rotation center axis provided on the base 11, and the flat plate portion 15 corresponding to the palm is perpendicular to the horizontal plane on which the base 11 is disposed. This is a drive mechanism having a function of moving up and down. In this way, the lifting actuator 12 moves the multi-joint portions 17 of the thumb, the index finger, and the middle finger at the same time at the same time by moving up and down the flat plate portion 15 corresponding to the palm, like a wrist. The operation can be reproduced.

As the elevating actuator 12, an appropriate small motor can be used. Here, a small stepping motor is used. The stepping motor can be rotated around the rotation center axis by a unit angle for each pulse signal as a drive signal. Accordingly, the number of pulses of the drive signal of the lift actuator 12 becomes the number of steps of lifting of the flat plate portion 15 corresponding to the palm, and the amount of lift can be controlled by the number of pulses of the drive signal.

The gripping actuator 14 has a function of independently driving the three multi-joint portions 17 that are rotatably attached to the flat plate portion 15 corresponding to the palm. Here, as shown in FIG. 1, the three multi-joint portions 17 have one joint that has one joint at the end of the flat plate portion 15 and can reproduce the movement of the thumb, and two index joints that have two joints. There are two that can reproduce the movement of the middle finger. One multi-joint portion 17 that reproduces the movement of the thumb and two multi-joint portions 17 that reproduce the movements of the index finger and the middle finger are arranged to face each other, like a human hand. Since these three multi-joint parts 17 will actually hold | grip with a target object, these can be considered as a holding part in a narrow sense.

Accordingly, the gripping actuator 14 internally drives the multi-joint portion 17 corresponding to the thumb, the multi-joint portion 17 corresponding to the index finger, and the multi-joint portion 17 corresponding to the middle finger. 3 actuators are included. Further, for example, the actuator of the multi-joint portion 17 system corresponding to the thumb has two sub-rotations that respectively perform two independent rotational drives that perform a rotational drive with respect to the flat plate portion 15 and a rotational drive of one joint portion ahead of the actuator. Including actuator. Since the multi-joint portion 17 actuator corresponding to the index finger and the multi-joint portion 17 actuator corresponding to the index finger have one more joint than the multi-joint portion 17 corresponding to the thumb, It includes three subactuators that perform independent rotational drive.

As the gripping actuator 14, an appropriate small motor can be used as in the lifting actuator 12. Here, a small stepping motor is used in the same manner as the lift actuator 12. As described above, the stepping motor can be rotated around the rotation center axis by a unit angle for each pulse signal as a drive signal.

Each multi-joint portion 17 has a plurality of joint portions, but at the final stage of gripping, a part of each multi-joint portion 17, for example, the most advanced joint portion of the multi-joint portion 17 corresponding to the thumb is rotationally driven. Often only. Therefore, at the final stage of gripping, the number of pulses of the driving signal of the gripping actuator 14 that drives the most advanced joint is the number of rotation steps of the most advanced joint of the multi-joint 17 corresponding to the thumb, for example. The amount or the magnitude of the gripping force can be controlled by the number of pulses of this drive signal.

The probe 20 is a component arranged one by one at the tip of the most advanced joint part of each of the three multi-joint parts 17 arranged facing each other. Each probe 20 constitutes a contact portion that actually touches and grips the object when the object is sandwiched by the three multi-joint portions 17, and detects contact and slippage with the object. And the sensor part for detecting the hardness of a target object is constituted.

FIG. 2 is a detailed view around the probe 20. The probe 20 has a contact / slip degree detection in which a vibrator 24 and a vibration detection sensor 26 are stacked on a first base 22 and a substantially hemispherical plastic contact ball 28 is further stacked thereon. The sensor part, the pressure detection sensor part on which the pressure sensor 34 is mounted on the second base 32, and the first base 22 of the contact / slip degree detection sensor part are provided. And a pressing ball 30 in contact with the surface. Each of these elements is integrated as a whole by the integrated resin portion 36. The probe 20 is fixed to the distal end portion of the most advanced joint portion of each multi-joint portion 17 by bonding or the like, with the second base 32 side of the pressure detection sensor portion being the bottom surface side.

The vibrator 24 has a function of making an incident wave incident on an object, and the vibration detection sensor 26 is an element having a function of detecting a reflected wave from the object. A piezoelectric element can be used for each of the vibrator 24 and the vibration detection sensor 26. That is, the former uses an electro-mechanical conversion function that generates an electric signal by inputting an electric signal, and the latter uses an electro-mechanical conversion function that generates an electric signal by inputting an electric vibration signal. it can.

FIG. 2 shows an input terminal 38 for supplying an electric signal to the vibrator 24 and an output terminal 40 for extracting an electric signal from the vibration detection sensor 26. The input terminal 38 and the output terminal 40 are connected to the contact / slip degree detection unit 50 by an appropriate signal line.

It should be noted that the stacking order of the vibrator 24 and the vibration detection sensor 26 is preferably such that the object side is the vibration detection sensor 26 as shown in FIG. 2, but this is reversed and the vibrator 24 is disposed on the object side. It is good also as what to do. In addition, the vibrator 24 and the vibration detection sensor 26 may not be stacked as shown in FIG. 2, but the vibrator 24 and the vibration detection sensor 26 may be arranged concentrically in some cases.

The contact ball 28 provided on the vibration detection sensor 26 is a member that is formed of a plastic resin such as nylon resin and has a function of smoothly pressing the object on its hemispherical surface. As the radius of the hemisphere, for example, about 5 mm can be used. The pressing ball 30 can also have the same configuration.

The pressure sensor 34 is an element having a function of detecting a pressing pressure when the probe 20 is pressed against an object. The pressing pressure has a function of supplementarily detecting that the probe 20 has contacted the object. Accordingly, in some cases, the pressure sensor 34 may be omitted.

As the pressure sensor 34, for example, a strain gauge can be used. When a strain gauge is used, it can be fixed to the second base 32 using a predetermined gauge adhesive or the like. When the pressure sensor 34 is a strain gauge, the resistance value changes according to the pressing pressure. Therefore, an appropriate signal line is connected to the terminals at both ends of the resistor, and the signal line is connected to the control unit 70, so that the control unit In 70, the pressing pressure can be calculated from the change in the resistance value.

The first base 22 is a fixed plate having a function of holding a laminated body of the vibrator 24, the vibration detection sensor 26, and the contact ball 28. The first base 22 can be formed of an appropriate substrate. In some cases, the first base 22 is provided with an input terminal 38 to the vibrator 24 and an output terminal 40 from the vibration detection sensor 26. can do.

Similarly, the second base 32 is a fixed plate having a function of holding the pressure sensor 34. The second base 32 can also be formed of an appropriate substrate. In some cases, the terminal of the pressure sensor 34 can be provided on the second base 32.

The integrated resin portion 36 is for wrapping the entire probe 20 in order to integrate the probe 20 as a whole. In this case, consideration is given so that vibrations of the vibrator 24 and the vibration detection sensor 26 are not excessively restricted. As this integrated resin part 36, it can be set as the structure which integrates the whole by a mold, for example using a silicon resin.

Returning to FIG. 1 again, the lifting actuator I / F 44 is an interface circuit provided between the lifting actuator 12 and the control unit 70. When the drive circuit is included in the lifting / lowering actuator 12, the lifting / lowering actuator I / F 44 can be configured by a buffer circuit, a waveform shaping circuit, a level shift circuit, and the like for matching signal levels. When the lift actuator 12 does not include the drive circuit, the lift actuator I / F 44 can include the drive circuit.

Similarly, the gripping actuator I / F 46 is an interface circuit provided between the plurality of gripping actuators 14 and the control unit 70. When each gripping actuator 14 includes its drive circuit, the gripping actuator I / F 46 is configured by a buffer circuit, a waveform shaping circuit, a level shift circuit, and the like for matching the signal level for each gripping actuator 14. it can. When each gripping actuator 14 does not include the drive circuit, the gripping actuator I / F 46 can include the drive circuit.

The contact / slip degree detection unit 50 is a circuit that is connected to each probe 20 and detects a gripping state between each probe 20 and an object. The contact / slip degree detection unit 50 is configured by a circuit provided for each probe 20, but since the contents of each circuit are the same, one contact / slip for one probe 20 will be described below. The contents of the slip detection unit 50 will be described.

The relationship between the probe 20 and the object includes a non-contact state where the object is not in contact with the probe 20 and a contact state where the object is in contact with the probe 20. The contact state includes a contact grip state in which the probe 20 and the target object are not relatively moved, and a so-called slip state in which the probe 20 and the target object are relatively moved. The contact / slip degree detection unit 50 has a function of distinguishing and detecting each of these states. Furthermore, the contact / slip degree detection unit 50 also has a function of detecting the hardness of the object in the contact gripping state.

FIG. 3 is a block diagram illustrating the configuration of the contact / slip degree detection unit 50. The contact / slip degree detection unit 50 includes a terminal 39 connected to the input terminal 38 of the transducer 24 in the probe 20 and a terminal 41 connected to the output terminal 40 of the vibration detection sensor 26. The contact / slip degree detection unit 50 is provided between an amplifier 52 whose input terminal is connected to the terminal 41, and an output terminal of the amplifier 52 and the terminal 39, and an input waveform to the vibrator 24 and a vibration detection sensor. When a phase difference occurs between the output waveforms from 26, a phase shift circuit 54 is provided for changing the frequency to shift the phase difference to zero.

When a phase difference occurs between the input waveform to the vibrator 24 and the output waveform from the vibration detection sensor 26, the phase shift circuit 54 changes the frequency of the input vibration to the vibrator 24 to make the phase difference zero. And the input frequency to the vibrator 24 when the phase difference becomes zero is output. In this manner, the phase shift circuit 54 outputs the input frequency f1 to the vibrator 24 that makes the phase difference related to the material property of the object zero, and this frequency f1 is first input to the vibrator 24. This is different from the input frequency f0 to the vibrator 24 when there is no phase difference between the waveform and the output waveform from the vibration detection sensor 26. Although accurate measurement of the phase difference is difficult, since the frequency change df can be measured with high accuracy, the material property of the object can be evaluated with high accuracy by this frequency change df.

The contents of the phase shift circuit 54 having such a function are described in detail in Japanese Patent Laid-Open No. 9-146991 which is the above-mentioned Patent Document 2. As described above, when a phase difference occurs between the input waveform to the vibrator 24 and the output waveform from the vibration detection sensor 26, vibration is incident on the object from the vibrator 24 and reflected from the object. For example, when the vibration detection sensor 26 detects the detected vibration.

In the above-mentioned patent document 2, it is described that the probe 20 is pressed against the object and the hardness, which is the material property of the object, is measured from the frequency change df. Occurs before and after contact with the object, and even if slip occurs between the probe 20 and the object, it occurs before and after the occurrence of the slip. Therefore, contact / slip between the probe 20 and the object can be detected by the frequency change df.

With such a configuration, a frequency change caused by a change in the contact relationship between the probe 20 and the object while maintaining a closed loop resonance state including the vibrator 24, the vibration detection sensor 26, and the object. df is detected by the df detection circuit 56. The detected df data is differentiated by the differentiating circuit 58 and transmitted from the terminal 59 to the control unit 70 as data indicating a contact / slip degree that is more sensitive than the df data.

Detected df data is converted into hardness data of the object by the hardness calculation unit 60 and transmitted to the control unit 70 via the terminal 61. In order to convert the frequency change df into the hardness of the object, for example, a calibration table or the like can be used. The calibration table can be created by pressing a reference material that can be used as a hardness reference against the tip of the contact ball 28 of the probe 20 and obtaining a frequency change df at that time. As the reference material, for example, a standard material such as silicon rubber having various hardnesses for which correspondence relationships with the Young's modulus representing the hardness and the shear elastic modulus are obtained in advance can be used. This function is already described in Patent Document 2.

The vibration frequency in the closed-loop resonance state including the vibrator 24, the vibration detection sensor 26, and the object can be changed by the phase shift circuit 54 so that the natural frequency having a high Q in the vibrator 24 can be changed. It is preferable to select a frequency other than. For example, when the primary natural frequency of the vibrator 24 is 1 MHz, it is preferable to avoid this frequency and set it to 400 kHz or the like.

How the contact / slip degree detection unit 50 detects and detects the contact relationship between the probe 20 and the object will be described with reference to FIGS. 4 and 5. FIG. FIGS. 4 and 5 are diagrams showing time changes in these four states, with time on the horizontal axis and four states on the vertical axis. As the four states, in each figure, in order from the top to the bottom, the number of steps of raising / lowering that is the number of steps of the driving pulse of the raising / lowering actuator 12, the number of steps of the gripping that is the number of steps of the driving pulse of the grasping actuator 14, and df detection The frequency change df, which is the output of the circuit 56, and df / dt, which is the output of the differentiating circuit 58. Here, the step number of the drive pulse of the gripping actuator 14 is shown for the actuator used for the rotation of the most advanced joint part of one multi-joint part 17 as the final stage of gripping.

FIG. 4 shows a contact state where the probe 20 contacts the target object from a non-contact state where the probe 20 and the target object are not in contact at all, and the probe 20 is moved up and down from that state to move the target object. It is a figure explaining a mode when it is going to lift. For example, it is a diagram showing changes in each state when an object placed on a workbench is sandwiched between a plurality of probes 20 and then the object is lifted from the workbench.

The time t0 is an initial state, and at this time, the probe 20 has no object and is not in contact at all. Therefore, there is no phase difference between the input waveform to the vibrator 24 and the output waveform from the vibration detection sensor 26, and no frequency change occurs in the phase shift circuit 54. That is, the frequency change df = 0.

At time t1, the gripping actuator 14 is driven to move toward the object, and the probes 20 provided at the most advanced joint parts of all the multi-joint parts 17 come into contact with the object and further advance. It's time. In this way, in order to bring the probe 20 into contact with the object, the multi-joint portion 17 that is a gripping part is driven to move with respect to the object, and this can be called control for gripping movement. .

As an example of an easy-to-understand explanation, at time t1, the multi-joint portion 17 corresponding to the index finger and the multi-joint portion 17 corresponding to the middle finger are moved and driven, and the respective probes 20 and the object are brought into contact with each other. This is when the most advanced joint part of the multi-joint part 17 corresponding to the thumb is moved from the state to be brought into contact with the object and further moved. In this case, the frequency change df in FIG. 4 indicates the state of the probe 20 provided in the multi-joint portion 17 corresponding to the thumb.

When the probe 20 comes into contact with an object, the phase difference occurs between the input waveform to the transducer 24 and the output waveform from the vibration detection sensor 26 at the moment of contact, and a frequency change occurs in the phase shift circuit 54. , Df detection circuit 56 outputs the frequency change df. Since the frequency change df is also a deviation from the frequency in the non-contact state, it indicates the frequency change from the frequency in the non-contact state.

Since the moment of contact is unstable, in order to detect contact reliably, the frequency change df is not the moment when the frequency changes even slightly from the frequency in the non-contact state, but a threshold is set in advance for the frequency change df, It is preferable to determine that the contact has been made when the detected df exceeds the threshold. That is, it is preferable to determine that the contact is made when the frequency exceeds a certain threshold from the non-contact state frequency in the non-contact state.

In this way, when the threshold value is set, strictly speaking, not the moment of contact, but when the probe 20 comes into contact with the object with some contact pressure corresponding to the threshold value and is in a light grip state, it is detected as a contact state. Will do. Therefore, this state is referred to as a contact gripping state, and the threshold value can be referred to as a contact gripping threshold frequency. That is, when the frequency changes from the non-contact state frequency exceeding the contact grip threshold frequency, the contact grip state is determined. When the threshold value is set for df, the frequency difference between the non-contact state frequency and the contact gripping threshold frequency becomes the df threshold value.

Since the contact pressure is determined by the contact gripping threshold frequency, the contact pressure can be increased or decreased by appropriately setting the contact gripping threshold frequency. For example, a gripping force of, for example, several grams, and in some cases a gripping force of 1 gram or less can be obtained.

In FIG. 4, df becomes the df threshold value at time t <b> 1, and the gripping state is reached, so the gripping actuator 14 stops gripping movement here. As a result, the object on the workbench is brought into contact and gripped by the plurality of multi-joint portions 17 that are gripping portions, and this state is maintained.

In FIG. 4, the number of gripping steps is maintained at a constant value from time t1 to time t2, and during that time, the gripping state between the gripping part and the object is continued as described above. At time t2, the number of ascending / descending steps is changed. Here, it is assumed that a lift command is issued to the lift actuator 12 to lift the object. Then, the object tends to be pulled upward from the workbench, but since the pressure when gripping is the contact pressure determined by the contact gripping threshold frequency, the gripping force obtained by multiplying the contact area by this contact pressure. Is smaller than the force in the gravitational direction based on the mass of the object, the object moves in the gravitational direction relative to the probe 20, and slip occurs between the probe 20 and the object.

When the slip occurs, the frequency changes from the frequency in the contact grip state without slip to the non-contact state frequency. FIG. 4 shows how the frequency change df changes toward zero again at time t2. The frequency change df gradually approaches zero as the number of steps to lift the target increases, and at time t3, the frequency change df = 0, that is, the frequency becomes a non-contact state frequency, and the probe 20 and the target It is shown that the relationship between the objects is in a non-contact state.

Such slip detection can be detected more reliably by the change in df / dt obtained by differentiating df with respect to time by the differentiating circuit 58 than with the frequency change df. Since the moment when the slip occurs is the moment when the frequency changes from the frequency when the contacted and gripped state is maintained, as shown in FIG. 4, df / dt suddenly changes from zero. Therefore, an appropriate threshold is set for df · dt, and when the threshold is exceeded, the occurrence of slipping can be detected.

FIG. 4 shows a case where the size of the number of gripping steps is maintained in a state in which contact gripping is detected. Therefore, depending on the setting of the contact gripping threshold frequency, as described above, the probe 20 and the target object Slip occurs between them. FIG. 5 is a diagram illustrating how the occurrence of slip is suppressed by changing the number of gripping steps when the occurrence of slip is detected. The contents of the horizontal axis in FIG. 5 and the contents of each state on the vertical axis are the same as those in FIG. The contents at times t0, t1, and t2 are the same as those in FIG. That is, the contents from time t0 to t2 are the same as in FIG.

It is the same as FIG. 4 that the number of lifting steps is changed at time t2 and a lifting command is issued to the lifting actuator 12 to lift the object. As indicated by df / dt, slip occurs between the probe 20 and the object at time t2.

Unlike the case of FIG. 4, here, the number of gripping steps is changed according to the magnitude of this slip. Specifically, when a slipping state is detected, the gripping actuator 14 changes the number of gripping steps in a direction in which the gripping actuator 14 returns the object from the slipping state to the contact gripping state according to the amount of change in the frequency output from the phase shift circuit 54. To do. That is, the gripping movement for moving the probe 20 toward the object side is controlled so as to increase the gripping force. This corresponds to slipping.

The change in the number of gripping steps is continued until the frequency output from the phase shift circuit 54 returns to the frequency in the contact gripping state. In FIG. 5, the change is continued so that the number of gripping steps is sequentially increased until time t4. And if it returns to the frequency in a contact gripping state, it will return to a contact gripping state, and since a slip state will no longer be detected, the change of the number of gripping steps is stopped and the state is maintained. At this time, the object is contact-gripped above the work table by the probe 20 with a contact pressure determined by the contact-gripping threshold frequency. That is, the object is gripped with the minimum gripping force.

Returning to FIG. 1 again, the control unit 70 has a function of controlling the operation of each element constituting the hardware part of the robot hand system 10 as a whole. As described above, the control unit 70 is connected to the lift actuator I / F 44, the gripping actuator I / F 46, and the contact / slip degree detection unit 50 through appropriate signal lines or the like. The control unit 70 is connected to an input unit 42 such as a keyboard and an output unit 43 such as a display and a printer. The control unit 70 can be configured by an appropriate computer or the like.

The control unit 70 includes a contact state stop module 72, a slip handling module 74, a grip maintaining module 76, and a hardness display module 78.

Here, the contact state stop module 72 has a function of executing processing at time t1 in FIGS. That is, the probe 20 is gripped and moved with respect to the object in a direction in which the object is not in contact with the probe 20 constituting the grasping unit, and the contact / slip degree detection unit 50 detects the probe. It has a function of stopping the gripping movement when contact gripping between the touch element 20 and the object is detected.

Further, the slip handling module 74 has a function of executing processing in a period from time t2 to t4 in FIG. That is, the object moves relative to the probe 20 in the gravitational direction while the contact movement is detected and the grip movement is stopped, and the contact / slip degree detection unit 50 detects the slip state. Sometimes, according to the amount of change in the frequency output by the phase shift circuit 54, the probe 20 constituting the gripper is further gripped and moved in a direction in which the probe 20 returns the object from the sliding state to the contact gripping state. It has a function.

Further, the grip maintaining module 76 has a function of executing processing at time t4 in FIG. That is, when the contact / slip degree detection unit 50 no longer detects a slipping state, it has a function of stopping the gripping movement of the probe 20 constituting the gripping unit.

Also, the hardness display module 78 has a function of displaying the hardness of the object at time t2 in FIG. 4 or time t4 in FIG. For example, in the case of time t4 in FIG. 5, the processing is executed by the function of the grip maintaining module 76, and the frequency change output by the phase shift circuit 54 when the contact / slip degree detection unit 50 no longer detects the slip state is detected. Based on this, it has a function of outputting the hardness of the object using the relationship between the frequency change and the hardness obtained in advance.

The above functions of the control unit 70 can be realized by software, specifically, by executing a robot hand control program. Of course, some of the functions realized by software may be realized by hardware.

The operation of the above configuration, in particular, the contents of each function of the control unit 70 will be described in detail with reference to FIGS. FIG. 6 and FIG. 7 are flowcharts showing a processing procedure for gripping an object with the minimum gripping force in the robot hand system 10. Each of these procedures corresponds to each processing procedure of the robot hand control program.

In order to execute processing for gripping an object with the minimum gripping force in the robot hand system 10, first, the robot hand system 10 is activated and a robot hand control program is started. Then, an object is set on the work table, and a grip command is acquired (S10). The grip command can be acquired via the input unit 42.

Next, the gripping actuator 14 is gripped and moved according to this gripping command. Here, as described above, first, the multi-joint portion 17 corresponding to the index finger and the multi-joint portion 17 corresponding to the middle finger are moved and driven to bring the respective probes 20 and the object into contact with each other. Further, the most advanced joint part of the multi-joint part 17 corresponding to the thumb is moved and driven to contact an object, and further moved and driven. In this case, the gripping actuator 14 for moving and driving the most advanced joint part of the multi-joint part 17 corresponding to the thumb is driven in units (S12). The unit driving corresponds to outputting one driving pulse of the stepping motor by advancing the number of gripping steps described in FIGS. 4 and 5 by one.

Next, it is determined whether or not contact gripping is detected (S14). Specifically, the contact / slip degree detection unit 50 compares the frequency output from the phase shift circuit 54 with a predetermined contact gripping threshold frequency, and when the frequency exceeds the contact gripping threshold frequency, the contact gripping Is detected. In other words, the probe 20 touches and grips the object when the frequency changes beyond the predetermined contact gripping threshold frequency from the non-contact state frequency when the probe 20 has no object. It is judged.

If the determination is negative in S14, the process returns to S12, and the gripping actuator 14 is further driven in units. That is, one stepping motor drive pulse is output. Then, the determination in S14 is performed again. This is repeated until the determination in S14 is affirmed. If the determination in S14 is affirmative, unit driving of the gripping actuator 14 is no longer performed. That is, the stop is performed in the contact gripping state (S16). The steps so far are executed by the function of the contact state stop module 72 of the control unit 70. The state of S16 is the state of t1 in FIGS.

After S16, the process proceeds to S20 in FIG. That is, an elevation command is acquired (S20). Actually, when a gripping command is acquired from the input unit 42 in S10, an elevation command, that is, an instruction to grip and lift the object is included. Until it is, the process of lifting the object is not performed. Therefore, the up / down command is a process that is handled as an internal process in the control unit 70 of the robot hand system 10 and that the process related to the up / down is executed when the state of S16 is entered.

When the elevating command is acquired, the elevating actuator 12 is driven in units according to this (S22). The meaning of the unit drive is the same as that described in S12. Here, one drive pulse is supplied to the stepping motor of the lift actuator 12. Thereby, the flat plate part 15 is lifted upward by a unit amount.

Then, the slip degree is detected (S24). Specifically, with respect to the frequency output from the phase shift circuit 54, the probe constituting the gripping portion when the frequency changes from the contact gripping state exceeding the contact gripping threshold frequency toward the non-contact state frequency. The object 20 is detected as a slipping state in which the object is slipping from the contact gripping state. More specifically, the change in frequency is acquired by the differentiating circuit 58 as df / dt.

Then, it is determined whether or not the slipping degree exceeds a predetermined threshold value (S26). The slip of the object with respect to the probe 20 occurs at the moment when the frequency output from the phase shift circuit 54 changes, but in reality, there is a limit to the detection accuracy of the frequency change. It is preferable to provide a threshold value. Specifically, a frequency that is a suitable frequency difference from the frequency in the contact gripping state is set as the threshold frequency, and when the frequency output from the phase shift circuit 54 changes from the frequency in the touch gripping state beyond the threshold frequency, the process of S26 is performed. Judgment can be affirmed.

4 and 5, when the output of the differentiation circuit 58 is used, an appropriate threshold is set for df / dt, and the determination in S26 is affirmed when the threshold is exceeded. It is good.

If the determination is negative in S26, the process returns to S22, and the lift actuator 12 is further driven in units. That is, one more drive pulse is supplied to the stepping motor of the lift actuator 12, and the number of lift steps is increased by one. Then, the determination of S26 is performed again through S24. This is repeated until the determination in S26 is affirmed.

If the determination in S26 is affirmative, the object moves relative to the probe 20 in the direction of gravity and slipping occurs, so the gripping actuator 14 is next driven unit-wise ( S28). The meaning of the unit drive of the gripping actuator 14 is the same as that described in S12. That is, the probe 20 is gripped and moved toward the target by further increasing the number of gripping steps by one.

Then, it is determined whether or not the slipping degree exceeds a threshold value (S30). This content is the same as S26. If the determination in S30 is affirmative, slipping is still continuing, so the process returns to S28 and the number of gripping steps is further increased by one. And determination of S30 is performed again. This is repeated until the determination in S30 is denied.

If the determination in S30 is negative, slipping is eliminated, and it is next determined whether or not the amount of elevation is less than the command value (S32). If the determination in S32 is affirmative, the object has not been lifted up to the first ascending / descending amount, so the process returns to S22 and the ascending / descending actuator 12 is further driven in units. That is, the number of lifting steps is further increased by 1, and the object is further lifted by a unit amount.

Then, when the affirmative from S24 is repeated and the slip is no longer caused, the determination of S32 is performed again. The above steps are repeated until the determination at S32 is negative. If the determination in S32 is negative, the lift amount is equal to or greater than the command value, and slipping is eliminated. That is, the object is lifted with a minimum gripping force and gripped without slipping.

Therefore, the change in the number of lifting steps and the change in the number of gripping steps are stopped, and gripping is continuously maintained in this state (S34). Based on the frequency output from the phase shift circuit 54 in that state, the hardness of the object is calculated by the hardness calculation unit 60 and displayed on the output unit 43 such as an appropriate display (S36).

In this way, by using the function of the phase shift circuit 54, contact detection and slip detection between the probe 20 and the object are performed, and the object does not cause relative movement in the direction of gravity. It can be gripped with the minimum gripping force. Further, the hardness of the object being held can be displayed.

The robot hand system having a gripping part according to the present invention can be used for a robot hand having a multi-joint finger that grips an object and carries it, for example, to an arbitrary place.

10. Robot hand system (having a gripping part), 11 base, 12 lift actuator, 13 arm, 14 gripping actuator, 15 flat plate part, 17 articulated part, 20 probe, 22 first base, 24 vibrator, 26 Vibration detection sensor, 28 contact ball, 30 pressing ball, 32 second base, 34 pressure sensor, 36 integrated resin part, 38 input terminal, 39, 41, 59, 61 terminal, 40 output terminal, 42 input part, 43 Output unit, 44 lifting actuator I / F, 46 gripping actuator I / F, 50 contact / slip degree detection unit, 52 amplifier, 54 phase shift circuit, 56 df detection circuit, 58 differentiation circuit, 60 hardness calculation unit, 70 control Part, 72 contact state stop module, 74 slip-compatible module, 76 gripping Lifting module, 78 hardness display module.

Claims

A gripper that moves relative to the object and grips the object;
A probe that is provided in the gripping unit and that has a vibrator that injects vibration into the object and a vibration detection sensor that detects a reflected wave from the object;
An amplifier having an input terminal connected to the output terminal of the vibration detection sensor;
When there is a phase difference between the input waveform to the transducer and the output waveform from the vibration sensor, it is provided between the output end of the amplifier and the input end of the transducer. A phase shift circuit that shifts the phase difference to zero and outputs the input frequency to the vibrator when the phase difference becomes zero,
Regarding the frequency output from the phase shift circuit, when the frequency changes beyond the predetermined contact grip threshold frequency from the non-contact state frequency when there is no target in the gripper, the gripper touches the target and grips it. A contact state detection unit for detecting
Regarding the frequency output by the phase shift circuit, when the frequency changes from the contact gripping state exceeding the contact gripping threshold frequency to the non-contact state frequency, the object changes from the contact gripping state to the gripping part. A slipping state detection unit for detecting a slipping state of sliding;
A control unit for controlling a gripping movement that is a relative movement of the gripping part with respect to the object;
With
The control unit
Grip when the gripping part is gripped and moved relative to the object in the direction of contact with the object from the state where the object is not in contact with the gripping part, and gripped when the contact state detection unit detects contact gripping between the gripping part and the object Contact state stopping means for stopping movement;
The phase shift circuit outputs when the object moves in the direction of gravity relative to the gripping part and the slipping state detection part detects the slipping state while detecting the gripping contact and stopping the gripping movement. A slip handling means for further gripping and moving the gripping part in a direction in which the gripping part returns the object from the slipping state to the contact gripping state in accordance with the amount of change in frequency to be performed;
Gripping maintaining means for stopping the gripping movement of the gripping part when the slipping state detecting unit stops detecting the slipping state;
A robot hand system having a gripping portion.
In the robot hand system having the grip portion according to claim 1,
The slip state detection unit includes a differentiation unit that differentiates the frequency output from the phase shift circuit, and performs slip detection based on a change in the frequency output from the phase shift circuit based on the output of the differentiation unit. Robot hand system having a part.
In the robot hand system having the grip portion according to claim 1,
Based on the frequency change output by the phase shift circuit when the slip state detection unit no longer detects the slip state in the processing of the grip maintaining means, the relationship between the frequency change and the hardness obtained in advance is used. A robot hand system having a gripping part, comprising a hardness output means for outputting the height.