Temporal variation output circuit

Abstract

To provide a temporal variation output circuit capable of directly acquiring temporal force variation values.SOLUTION: A temporal variation output circuit is provided, comprising a differential amplifier circuit configured to receive values acquired by a sensor for acquiring contact force with a target object and a current variation value due to inductance of the sensor value as input and output temporal variation values of the contact force with the target object.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a time-varying output circuit. [Background technology]

[0002] Robot hands with fingers are controlled by detecting the force acting on an object from the fingertips using, for example, a six-axis sensor attached to the fingertips or a contact sensor attached to the finger pads, and controlling the force acting on the object so that it matches a target acting force (see, for example, Patent Document 1).

[0003] When grasping an object with the fingers, depending on the shape of the object, in addition to the point contact state between the object and the fingertip, grasping control is required in both the rolling contact state where the object is grasped while rolling (the object is rolling), and the sliding contact state where the object slides. In the point contact state and the rolling contact state, the posture of the grasped object can be determined from contact information (contact force and contact point) alone.

[0004] On the other hand, in a sliding contact state, contact information alone is insufficient for posture estimation. Therefore, in order to suppress the sliding contact state, the physical parameters must be known. Alternatively, to suppress the sliding contact state, a control method that does not take the sliding situation into account has been used. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 589103 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if attempts were made to use the time change in force for control that takes slippage into account, conventional technology, for example, when using an event camera, could only acquire changes in the image, and could not directly acquire the time change in force. For this reason, conventional technology has made it difficult to achieve stable grip in sliding contact that involves slippage.

[0007] The present invention has been made in consideration of the above-mentioned problems, and has as its object to provide a time change output circuit that can directly obtain the time change value of a force. [Means for solving the problem]

[0008] (1) In order to achieve the above object, a time-varying output circuit according to one aspect of the present invention is configured to output a value (e.g., V + ) and the value of the sensor is the current change value due to inductance (for example, V - ) and a differential amplifier circuit that receives the input of the contact force with the target object and outputs a time-varying value of the contact force with the target object.

[0009] (2) In the time-varying output circuit according to one aspect of the present invention described above in (1), one end of the sensor may be connected to a power supply voltage, one end of the inductance may be connected to the other end of the sensor and the positive input terminal of the differential amplifier circuit, and the other end may be connected to the negative input terminal of the differential amplifier circuit and grounded, and the differential amplifier circuit may output a time-varying value of force obtained by multiplying the difference between the value input to the positive input terminal and the current change value input to the negative input terminal by the gain of the differential amplifier circuit.

[0010] (3) The time-varying output circuit according to one aspect of the present invention described above in (1) may further include a resistor and a buffer circuit, and the input of the current change value due to the inductance of the sensor value may be grounded via the resistor and connected to the input of the buffer circuit, and the buffer circuit may output the contact force with the target object.

[0011] (4) In the time-varying output circuit according to one aspect of the present invention described in (3) above, one end of the sensor is connected to a power supply voltage, one end of the inductance is connected to the other end of the sensor and the positive input terminal of the differential amplifier circuit, and the other end is connected to the negative input terminal of the differential amplifier circuit, one end of the resistor, and a first input terminal of the buffer circuit, the other end of the resistor is grounded, the differential amplifier circuit outputs a time-varying value of force obtained by multiplying the difference between the value input to the positive input terminal and the current change value input to the negative input terminal by the gain of the differential amplifier circuit, and the buffer circuit may have two input terminals and an output terminal connected to each other and output the contact force with the target object.

[0012] (5) In the time-varying output circuit according to any one of the above (1) to (3) aspects of the present invention, the sensor may be a sensor whose resistance changes in response to an applied force. [Effects of the Invention]

[0013] According to the above (1) to (5), the time change value of the force can be directly acquired. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are diagrams for explaining point contact and rolling contact in which no slippage occurs; [Figure 2] This is an image diagram of the contact points between the target object and the fingers of the end effector in sliding contact, the forces acting from the fingertips to the target object, and the forces acting on the target object. [Figure 3] 10A and 10B are diagrams showing models and high-speed conditions in each contact state. [Figure 4] This is a model to explain the problems with conventional methods. [Figure 5] FIG. 1 is a diagram illustrating the relationship between position and energy, which explains the problems of the conventional method. [Figure 6] FIG. 2 is a diagram illustrating an example of a time-varying output circuit according to an embodiment. [Figure 7] FIG. 1 is a diagram illustrating an example of the configuration of a control system including a time-varying output circuit. [Figure 8] FIG. 10 is a diagram illustrating an example of sensor output. [Figure 9] 10A and 10B are diagrams illustrating an example of a change in force applied to a sensor, a force differential value, and a change in the output of a differential amplifier circuit. [Figure 10] FIG. 10 is a side view of the hand during gripping. [Figure 11] This is an example of a gripping operation using point contact and rolling contact in the conventional method. [Figure 12] This shows the change in the direction of force over time and the change in velocity at the contact point over time in the grasping operation using point contact and rolling contact in the conventional method. [Figure 13] 10 shows an example of a change in the direction of force with respect to time, and an example of a change in force and a change in a force differential value with respect to time during control in a conventional method. [Figure 14] 10A and 10B are examples of gripping operations using point contact, rolling contact, and sliding contact according to an embodiment. [Figure 15] 10 shows the change in the direction of force over time and the change in velocity at the contact point over time in the gripping operation with point contact, rolling contact, and sliding contact in the embodiment. [Figure 16] 10 shows an example of a change in the direction of force with respect to time, a change in force with respect to time, and a change in a force differential value during control in the method of the embodiment. [Figure 17] 10A and 10B are diagrams illustrating an example of control according to a conventional technique and control according to a modified example of the present embodiment in which the force command is offset and the gain is increased or decreased. [Figure 18] FIG. 10 is a diagram illustrating a modified example of the time-varying output circuit according to the embodiment. [Figure 19] 4 is a flowchart of a process of a control system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used in the following description, the scale of each component is appropriately changed so that each component can be recognized. In all the drawings for explaining the embodiments, the same reference numerals are used for components having the same functions, and repeated explanations will be omitted. Furthermore, in this application, "based on XX" means "based on at least XX," and includes cases where it is based on other elements in addition to XX. Furthermore, "based on XX" is not limited to cases where XX is used directly, but also includes cases where it is based on XX that has been calculated or processed. "XX" is any element (for example, any information).

[0016] [overview] First, the terms "point contact," "rolling contact," and "sliding contact" used in this embodiment will be explained. FIG. 1 is a diagram for explaining point contact and rolling contact where no slip occurs. The diagrams indicated by symbols g11 and g12 are examples of point contact states. The diagram indicated by symbol g12 is an enlarged view of the gripping state indicated by symbol g11. The arrow g13 shows an image of the force acting from the fingertip to the target object and its direction. The diagram g21 shows an example of a rolling contact state, with arrow g22 indicating an image of the fingertip rolling on the target object.

[0017] Conventional control methods stabilize the dynamics of an object based on its estimated CoM (weight). Grasping control requires precise joint forces that are non-slip, but this is difficult. The prerequisite for control of point contact and rolling contact is that point contact ∈ rolling contact, and the posture of the grasped object is estimated and controlled using only contact information between the contact point of the fingertip and the contact point of the target object.

[0018] Figure 2 is an image diagram of the contact points between the target object obj and the fingers fin (fin-1 to fin-3) of the hand during sliding contact, as well as forces f1 to f3 acting from the fingertips to the target object obj and forces f5 to f6 acting on the target object obj. Note that although Figure 2 shows an example with three fingers, the number of fingers may be two or more. The prerequisite for control that also uses sliding contact is that point contact ∈ rolling contact ∈ sliding contact, and contact information alone is insufficient to estimate the posture of the target object, making stable grasp control difficult.

[0019] In the following example, the hand may be controlled remotely by an operator wearing a head-mounted display, a data glove, or the like. However, the operation control is not limited to remote control, and may be performed while the operator visually checks the hand and the target object, or the hand may be controlled automatically.

[0020] FIG. 3 shows the model and constraint conditions in each contact state. The diagram g31 is an image diagram of the contact points between the target object obj and the fingers fin of the hand 2, the forces acting from the fingertips to the target object obj, and the forces acting on the target object obj. The figure with reference symbol g32 is an example model of the finger fin and the target object obj during point contact control. The constraint conditions in this case are no rolling and no sliding. Conventional control methods could only handle two or more point contacts. The figure with reference symbol g33 is an example of a model of the finger fin and the target object obj during control in rolling contact. The constraint condition in this case is rolling but no sliding. This could also be handled by conventional control methods. The figure with reference symbol g34 is an example of a model of the finger fin and the target object obj during control in slipping contact. The constraint conditions in this case include both rolling and sliding, which could not be handled with conventional control methods.

[0021] It should be noted that the gripping portion in this embodiment is controlled without using images captured by the imaging device.

[0022] The control method of this embodiment will be described. First, the problems with the conventional method will be explained. Figure 4 is a model for explaining the problems with the conventional method. Figure 5 is a diagram showing the relationship between position and energy, which explains the problems with the conventional method. In Figure 5, the horizontal axis represents position and the vertical axis represents energy. In the conventional method, all the energy generated by the finger E all is the dissipative energy E as shown in the following equation (1). disspatuve and the conserved energy E coserved It is expressed in terms of

[0023]

number

[0024] Conserved energy E coserved The term is expressed as the kinetic energy E kinetic and the potential energy E potential It is expressed in terms of

[0025]

number

[0026] In the conventional method, the conserved energy E potential The problem is that it is a function that depends on the position and orientation, as shown in Figure 5, and it can only control point contact and rolling contact, but cannot control sliding contact.

[0027] In contrast, in this embodiment, the stored energy E potential The gravitational energy E gracity and external force Eadd By expressing it in terms of

[0028]

number

[0029] In this way, in this embodiment, the external force E addThe term includes slip information, making the system integrable, i.e., conservative. The external force E that satisfies this condition add An example of this equation is the following equation (4). This allows the shape of the potential function to be implicitly known, and Lyapunov stability can be achieved. In this embodiment, equation (4) is expressed as "f tip " and "f" and simplified to "p · tip " to "p · " and simplify it to E add =∫(f p · )dt.

[0030]

number

[0031] Equation (4) is a time integral. The time integral of the force often contains slip information. In the embodiment, f tip is the force of the fingertip at the contact point, and p tip is the position of the contact point (the position of the fingertip). · With f · tip is the change in fingertip force, and p · tip is the change in position of the contact point.

[0032] The stability condition is the external force term E add includes slip information, and the external force term E add is integrable (the system is a conservative system), and in this case, the force derivative, which is the time change value of the force, is required. External force term E add includes slip information, and the external force term E add To satisfy the condition that p is integrable (the system is a conservative system), · tip For example, this is expressed by the following equation (5).

[0033]

number

[0034] Equation (5) is add =∫(f p · )dt, equation (4) can also be expressed as the following equation (6).

[0035]

number

[0036] Furthermore, the stability of an autonomous system can be divided into Lyapunov stability and near-near stability. For any s, if δ exists and ||x(0)||<δ, then if ||x(t)||<ε, then the equilibrium point x=0 is Lyapunov stable. In other words, when an orbit that starts from near an equilibrium point of a dynamical system continues to remain near the equilibrium point, the equilibrium point is said to be Lyapunov stable.

[0037] [Getting force derivatives] The following methods can be considered as methods for directly obtaining the above-mentioned force differential values. (Example 1) Using an event camera When an event camera is used, only the changing parts can be acquired in the image, but it is difficult to directly acquire the force differential value. (Example 2) Using a software event-driven sensor value acquisition circuit This method is intended to reduce the amount of data transferred, and since it only detects contact with the tactile sensor, stores the previous value, and performs calculations using software, it has low responsiveness and places a heavy load on the calculation device. (Example 3) Using a hardware event-driven sensor value acquisition circuit This method is an improvement over (Example 2) and uses analog circuits for calculations. However, it requires saving the previous value, which requires additional memory circuits. Furthermore, it takes time to read the previous value. With the above method, it is difficult to realize a high-response, small-sized system.

[0038] For this reason, in this embodiment, a force differential value is generated using the time change output circuit 32. Then, in this embodiment, the force differential value generated by the time change output circuit 32 is used to perform control when slippage occurs.

[0039] FIG. 6 is a diagram showing an example of a time-varying output circuit according to this embodiment. 6, the time variation output circuit 32 includes, for example, an inductance L and a differential amplifier circuit 321. The time variation output circuit 32 acquires a detection value from the sensor 23 included in the hand 2.

[0040] One end of the sensor 23 is connected to a power supply voltage VDD. The inductance L is connected at one end to the other end of the sensor 23 and the positive input terminal V of the differential amplifier circuit 321. + , and the other end is connected to the negative input terminal V of the differential amplifier circuit 321. - and is grounded (GND). The differential amplifier circuit 321 has a positive input terminal V + and the value input to the negative input terminal V - The output Vout obtained by multiplying the difference between the current change value input to the differential amplifier circuit 321 and the gain α of the differential amplifier circuit 321 is output to the control unit 33. The output of the differential amplifier circuit 321 is a force differential value. In other words, the differential amplifier circuit 321 receives a value (for example, V + ), and the value of the sensor 23 is the change value of the current flowing through the inductance L (for example, V - ) are input. The differential amplifier circuit 321 then outputs the time change value of the contact force with the target object.

[0041] Sensor 23 is, for example, a pressure-sensitive resistive tactile sensor whose resistance changes in response to an applied force, such as a load cell, which is a sensor that detects force (mass, torque), and has a variable resistance value r. The detected value is expressed as F=f(r). The pressure-sensitive resistive tactile sensor may also be a thin-film pressure-sensitive sensor.

[0042] The inductance L detects the current change (di / dt). The differential amplifier circuit 321 detects the change in the current flowing across the inductance L, V + (-V - ) = -L(di / dt) is input. If the gain of the differential amplifier circuit 321 is α, the output Vout of the differential amplifier circuit 321 is given by the following equation (7). This output is df / dt, i.e., the force differential value. The value of inductance L and gain α are determined by experiment or simulation depending on, for example, the characteristics of the sensor, the target object, the work content, etc.

[0043]

number

[0044] As a result, in this embodiment, the time change value of the force can be directly measured and generated by an analog circuit using the inductance L of the time change output circuit 32. And, according to this embodiment, since the circuit configuration is an analog circuit, responsiveness is high. Furthermore, the circuit configuration of this embodiment does not require a circuit for saving or reading the previous value of the force as in the example described above, and can be made smaller.

[0045] [Example of a system with a time-varying output circuit] Next, an example of a system with a time-varying output circuit will be described. 7 is a diagram showing an example of the configuration of a control system including a force differential value acquisition circuit. As shown in FIG. 7, a control system 1 includes, for example, a hand 2 and a control device 3. The hand 2 includes, for example, a plurality of fingers 21 (21-1, ..., 21-n) (n is an integer of two or more) (movable parts), a plurality of actuators 22 (22-1, ..., 22-n), a plurality of sensors 23 (23-1, ..., 23-n), and a base 24. The control device 3 includes, for example, an acquisition unit 31, a time variation output circuit 32, a control unit 33, a drive circuit , an output unit 35, and a storage unit .

[0046] The hand 2 is, for example, an end effector or a gripper. The hand 2 has at least two fingers 21. Alternatively, each hand 2 may have at least one finger. The hand 2 grasps, for example, a target object under the control of the control device 3. The hand 2 may be one arm or both arms, and may have an arm and a body. The hand 2 may also be included in, for example, a robot having a body. The hand 2 and the control device 3 are connected to each other via a wired or wireless network NW.

[0047] The fingers 21 (21-1, . . . , 21-n) have joints.

[0048] The actuators 22 (22-1, . . . , 22-n) are attached to the joints of the finger portion 21 and the joints between the finger portion 21 and the base portion 24. The actuators 22 may include a drive circuit .

[0049] The sensors 23 (23-1, ..., 23-n) are, for example, finger pressure sensors attached to the pads of the fingers 21 or six-axis sensors attached indirectly. The six-axis sensor detects forces along three axes (x, y, z) and moments along three axes (α, β, γ).

[0050] The base 24 is the part to which the fingers 21 are attached.

[0051] The control device 3 uses information acquired from the hand 2 to control the hand 2 and a contact object (for example, a grasped object or a floor surface) that comes into contact with the finger portions 21 of the hand 2.

[0052] The acquisition unit 31 acquires the detection information detected by the sensor 23 of the hand 2 .

[0053] The time variation output circuit 32 receives the detection value of the sensor 23 acquired by the acquisition unit 31 as an input and outputs a force differential output to the control unit 33. Note that the time variation output circuit 32 may be provided for each sensor 23, for example, or the detection value of the sensor 23 may be temporarily stored in the storage unit 36 ​​and processed in a time-division manner.

[0054] The control unit 33 generates a control value for controlling the hand 2 using the force differential output output by the time change output circuit 32.

[0055] The drive circuit 34 outputs a drive signal for driving the corresponding actuator 22 to the output unit 35 in accordance with the control value generated by the control unit 33. The drive circuit 34 may be provided in the hand 2.

[0056] When the control device 3 includes a drive circuit 34, the output unit 35 outputs the control value generated by the control unit 33 to the hand 2. When the hand 2 includes a drive circuit 34, the output unit 35 outputs the drive signal generated by the drive circuit 34 to the hand 2.

[0057] The storage unit 36 ​​stores programs, thresholds, mathematical expressions, identification information for identifying the hand 2, and the like, which are necessary for control.

[0058] 7 is merely an example and is not limiting. Other components may be included. For example, the hand 2 and the control device 3 each include a power supply unit.

[0059] [Example of sensor output, example of force derivative] Next, examples of the output of the sensor 23 and examples of the force differential value will be described. Fig. 8 is a diagram showing an example of sensor output. The horizontal axis represents the force applied to sensor 23, and the vertical axis represents the resistance value. Symbol g51 represents a first force applied to sensor 23, and symbol g52 represents a second force applied to sensor 23 that is greater than the first force. As shown in Fig. 8, the smaller the force applied to sensor 23, the greater the resistance value, and vice versa.

[0060] FIG. 9 is a diagram showing an example of changes in the force applied to the sensor, the force differential value, and the output of the differential amplifier circuit. Graph g60 is an example of the change in force over time. In graph g60, the horizontal axis represents time and the vertical axis represents force. Graph g70 is an example of the change in the force derivative di / dt over time. In graph g70, the horizontal axis represents time, and the vertical axis represents the force derivative di / dt. Graph g80 is an example of a change in the output Vout of the differential amplifier circuit over time. In graph g70, the horizontal axis represents time, and the vertical axis represents the output Vout of the differential amplifier circuit.

[0061] As shown in the graph of reference symbol g60, the period from time t1 to t2 is a period during which, for example, a first force is applied, and the period from time t2 onwards is a period during which, for example, a second force is applied. This change in force was detected by the time change output circuit 32, and as a result, as shown in the graphs with symbols g70 and g80, at times t1 and t2 when the force changed, the force differential value and the output of the differential amplifier circuit increased in accordance with the applied force. The examples of outputs and changes shown in FIGS. 8 and 9 are merely examples, and the present invention is not limited to these.

[0062] [Example of gripping operation in a conventional method and example of gripping operation in this embodiment] Next, an example of a gripping operation using point contact and rolling contact according to a conventional method and an example of a gripping operation using point contact, rolling contact, and sliding contact according to this embodiment will be described. Fig. 10 is a side view of the hand during grasping. The example in Fig. 10 is an image diagram showing the hand 2 attempting to stably grasp the target object obj with two fingers 21 (21-1, 21-2). The target object obj is an object whose upper diameter is smaller than its lower diameter, such as a cup placed with its mouth facing downwards. The circles 25 (25-1-1, 25-1-2, 25-2-1, 25-2-2) represent joints. Points g101 and g102 represent contact points between the finger 21 and the target object obj. A line g103 indicates a tangent direction to the target object obj, a line g104 indicates a normal direction to the target object obj, and a dashed arrow g105 indicates a force generated from the contact points (points g101 and g102) on the finger 21. Note that the direction of the arrows may be reversed.

[0063] The method for confirming the gripping operation by point contact and rolling contact of the conventional method and the gripping operation by point contact, rolling contact, and sliding contact of this embodiment is as follows. (A) Static gripping with a specific internal force (5 N) applied. (B) Apply an input (disturbance) that exceeds the static friction region. The criteria for determining whether a grasp is successful or unsuccessful are as follows: (Success) After passing through the static friction region, it returns to the static friction region again. (Failure) After passing the static friction region, it never returns to the static friction region.

[0064] In addition, conventional grip control uses, for example, compliance control. For this reason, rolling constraints are set as a prerequisite, and control is performed at the contact point on the manipulated object side. In the following explanation, the subscript cmd indicates the target control value (target angle and position value) sent to the actuator. The target force value in conventional methods is f cmd is expressed by the following equation (8). ref and p act Each of these is a fixed value. In equation (8), k p is the gain and p re f is the target position of the finger, the position of the contact point, and p act is the position of the contact point between the fingertip and the target object. The stability is Lyapunov stable, and the target energy E cmd is expressed as the following equation (9).

[0065]

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[0066]

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[0067] FIG. 11 shows an example of a grasping operation using point contact and rolling contact according to a conventional method. Note that FIG. 11 is a simulation result. Reference symbol g201 indicates the start of grasping, reference symbol g202 indicates the state in which force is applied, and reference symbol g203 indicates the state in which the target object obj has slipped off the finger 21. Reference symbol 211 indicates the forces and axes generated in each finger 21 of reference symbol 201. Reference symbol 212 indicates the forces and axes generated in each finger 21 of reference symbol 202. Reference symbol 213 indicates the forces and axes generated in each finger 21 of reference symbol 203. Note that in reference symbols g201 to g203 and g211 to g213, each line indicates the axial direction, the force acting from the fingertip to the target object, etc. In the conventional grasping operation using point contact and rolling contact, the target object obj slips off the finger 21 and cannot be maintained by the finger 21, as shown by the symbol g203.

[0068] Figure 12 shows the change in the direction of force over time and the change in velocity at the contact point over time in grasping operations using point contact and rolling contact in the conventional method. Note that Figure 12 is a simulation result. The horizontal axis of reference symbol g230 is time (sec), and the vertical axis is the angle θ of the force generated at the contact point. The angle θ is the angle between the normal direction of the target object obj and the perpendicular line, as shown in Figure 10. The horizontal axis of reference symbol g240 is time (sec), and the vertical axis is the velocity (m / s) generated at the contact point.

[0069] Reference symbol g220 indicates the state of the finger portion 21. Reference symbol g221 indicates the start of grasping, reference symbol g222 indicates the state in which force is applied, and reference symbol g223 indicates the state in which the target object obj has slipped off the finger portion 21.

[0070] Reference symbol g230 indicates the change in the direction of the force over time. Region g231 is a zone where slippage occurs but the frictional force is not exceeded and grip is maintained (static friction region), region g232 is a zone where the frictional force exceeds the gripping force, and region g233 is an error zone. The angle θ indicated by arrow g234 indicates that grip is maintained in the gripping state indicated by reference symbol g221. The angle θ indicated by arrow 235 indicates that the frictional force has been exceeded and the angle is changing rapidly. The angle θ indicated by arrow 236 indicates that the target object obj has slipped off the finger 21 and cannot return to the finger 21.

[0071] Symbol g240 represents the change in velocity at the contact point over time. Between 0.8 and 1.0 seconds, as shown by symbol g230, the angle of force changes suddenly, indicating that slippage is occurring.

[0072] As described above, with conventional control methods, the robot would not return to the static friction region after going beyond it, and so it was unable to maintain grip (failure), making stable grip beyond the static friction region impossible. In addition, in the control using the conventional method, the stable region (maximum target internal force value - minimum target internal force value) was approximately 0.2 (N).

[0073] Figure 13 shows an example of the change in the direction of force over time, and the change in force and force derivative over time when controlled using a conventional method. The horizontal axis is time (msec), and the vertical axis is force and force derivative. The graph with reference symbol g250 shows the change in force (N) over time. The graph with reference symbol g260 shows the change in force derivative (N) over time. When the force differential value is negative as shown by the dashed circle g261, the force is released and the object is slipping as shown in the period from 0.8 to 1.0 indicated by reference symbol g240 in FIG. Furthermore, during the period of error region g241 of graph g240 in FIG. 8, the force differential value changes, but because control is not performed using the force differential value, the fingertip continues to slide and the fingertip velocity fluctuates.

[0074] FIG. 14 shows an example of a grasping operation using point contact, rolling contact, and sliding contact according to this embodiment. Note that FIG. 14 shows simulation results. Reference symbol g301 indicates the start of grasping, reference symbol g302 indicates a state in which force is applied, and reference symbol g303 indicates a state in which the fingers 21 are maintaining a grasp of the target object obj. Reference symbol 311 indicates the forces and axes generated in each finger 21 indicated by reference symbol 301. Reference symbol 312 indicates the forces and axes generated in each finger 21 indicated by reference symbol 302. Reference symbol 313 indicates the forces and axes generated in each finger 21 indicated by reference symbol 303. Note that in reference symbols g301 to g303 and g311 to g313, each line indicates an axial direction, a force acting from the fingertip to the target object, etc. In the gripping operation using point contact, rolling contact, and sliding contact in this embodiment, the finger 21 can maintain a grip on the target object obj, as indicated by the reference symbol g303.

[0075] Figure 15 shows the change in the direction of force over time and the change in velocity at the contact point over time in a gripping operation using point contact, rolling contact, and sliding contact in this embodiment. Note that Figure 15 is a simulation result. The horizontal axis of symbol g330 is time (sec), and the vertical axis is the angle θ of the force generated at the contact point. The horizontal axis of symbol g340 is time (sec), and the vertical axis is the velocity (m / s) generated at the contact point.

[0076] Reference symbol g320 indicates the state of the finger portion 21. Reference symbol g321 indicates the start of grasping, reference symbol g322 indicates the state in which force is applied, and reference symbol g323 indicates the state in which the target object obj does not slip off the finger portion 21 and can be maintained in grasp.

[0077] Symbol g330 represents the change in the direction of the force over time. Region g331 is the zone where slippage occurs but the friction force is not exceeded and grip is maintained (static friction region), and region g332 is the zone where the friction force exceeds the grip force. The angle θ indicated by the arrow g334 indicates that the grip is maintained in the grip state indicated by the symbol g321. The angle θ indicated by the arrow 335 indicates that the friction force is exceeded and the angle is changing rapidly. The angle θ indicated by the arrow 336 indicates that the target object obj does not slip off the finger 21, but returns to the static friction region, and the target object obj returns to the finger 21.

[0078] Symbol g340 represents the change in velocity at the contact point over time. Between 0.4 and 0.6 seconds, the angle of force changes suddenly, as shown by symbols g330 and g340, indicating that slippage is occurring.

[0079] In this way, with the control of this embodiment, after going beyond the static friction region, the object returns to the static friction region, maintaining (successfully) the grip, and making it possible to achieve stable grip beyond the static friction region. In the control of this embodiment, the stable region (maximum target internal force value - minimum target internal force value) is approximately 4.0 (N), which is approximately 20 times larger than the control of the conventional method.

[0080] Figure 16 shows an example of the change in force direction over time, and the change in force and force derivative over time during control using the method of this embodiment. The horizontal axis represents time (msec), and the vertical axis represents force and force derivative. The graph with reference symbol g350 shows the change in force (N) over time. The graph with reference symbol g360 shows the change in force derivative over time. The force differential value in the area surrounded by the chain circle g261 is negative, but whereas in the prior art it drops to about -6, in this embodiment it is possible to quickly detect that it has become negative at about -3.5.

[0081] As a result, according to this embodiment, changes in the force differential value are detected, as in the period from 0.4 to 0.6 (msec) in the graph of reference symbol g340 in Fig. 15, and energy control is performed using the detected changes in the force differential value, so that the target object can be continuously grasped without slipping off. Furthermore, according to this embodiment, there is no fluttering of the fingertip speed, as occurs with conventional control methods.

[0082] (Variation) 17 is a diagram showing an example of control performed by a conventional technique and control performed by a modified example of this embodiment in which the force command is offset and the gain is increased or decreased. The target object obj is an image of an object such as a small rock with an irregular shape, for example. The graph of symbol g520 shows the relationship between the command force and the Lyapunov function. The range of symbol g521 is the static friction region (friction that occurs on a stationary object). The range of symbol g522 is the dynamic friction region (friction that occurs on a moving object). Symbol g523 is the sliding boundary. The dashed line g524 represents the relationship of the Lyapunov function to the command force in the static friction region, while the lines g525 and g526 represent the relationship of the Lyapunov function to the command force in the dynamic friction region.

[0083] In this prior art, for example, compliance control, as shown by symbol g520, the friction element is pulled into the minimum point g527 of the boundary line g523 between the static friction region and the dynamic friction region and stabilizes. That is, the friction element tends to slip slightly as shown by line g524, but stabilizes at the boundary line g523 and cannot return. The problem with this prior art technology is that the object motion is stable due to stabilization at the slip boundary g523, but the object motion is violent due to excessive control input.

[0084] In the prior art, slippage information f · act Calculate the force command from the energy expression including · cmd is expressed in a non-slip form as follows:

[0085]

number

[0086] And the target force instruction f cmdis expressed as in the following equation (11): In equation (11), PI represents PI (Proportional-Integral) control.

[0087]

number

[0088] In contrast to this, in the modified example, in order to extract the change during slippage, the control unit 33A offsets the force command as shown in the following equations (12) and (13). In this way, in this embodiment, since the error component is subtracted, only the change during slippage can be extracted and controlled.

[0089]

number

[0090]

number

[0091] The offset is defined as the target value of the energy change E · cmd f in Eq. (10) act and f · act From this, f is obtained as shown in equation (13). error and f · error and replace with f error f as in equation (12). cmd and f act In the control of the conventional technique using equation (10), act On the other hand, in the control of the present embodiment using the formula (13), the curve converges to the minimum value g527 as shown in the formula (12). cmd From f act By offsetting (subtracting) this, it is possible to control the curve so that line g574 is at the bottom, rather than converging at the boundary line like lines g574 and g575 on the graph of symbol g570.

[0092] Furthermore, in the modified example, in order to make the change gentler, the control unit 33A uses a command E · cmd From the change in the gain k f Update by increasing or decreasing k e is the gain and is a fixed value.

[0093]

number

[0094] The graph of symbol g570 is the relationship between the command force and the Lyapunov function. The range of symbol g571 is the static friction region. The range of symbol g573 is the dynamic friction region. Symbol g573 is the sliding boundary. The dashed line g574 represents the relationship of the Lyapunov function to the command force in the static friction region, and the line g575 represents the relationship of the Lyapunov function to the command force in the dynamic friction region.

[0095] In the control of the modified example, when the boundary between the static friction region and the dynamic friction region is crossed, the change is controlled gradually as indicated by arrow g576, allowing for continued grip as indicated by reference symbol g554. As a result, even at the boundary position, the change is not a minimum value represented by a steeply inclined line as in the graph represented by reference symbol g520, but a gradual change as indicated by arrow g576 in the graph represented by reference symbol g570. In addition, in the modified example, control is performed to remain within the static friction region where a stable grip can be maintained. This control solves the problems of the conventional technology. In this modified example, in addition to the force differential value, force (f) is also required. For this reason, in the modified example, force (f) is also detected by a time-varying output circuit.

[0096] FIG. 18 is a diagram showing a modification of the time variation output circuit of this embodiment. The time variation output circuit 32A includes, for example, an inductance L, a differential amplifier circuit 321, a buffer circuit 322, and a resistor R. The time variation output circuit 32A acquires a detection value from the sensor 23 included in the hand 2.

[0097] One end of the sensor 23 is connected to a power supply voltage VDD. The inductance L is connected at one end to the other end of the sensor 23 and the positive input terminal V of the differential amplifier circuit 321. + , and the other end is connected to the negative input terminal V of the differential amplifier circuit 321. - , connected to a first input terminal of a buffer circuit 322, and connected to one end of a resistor R. The other end of the resistor R is grounded (GND).

[0098] The buffer circuit 322 has a second input terminal connected to an output terminal, and the output terminal connected to the control unit 33A. The buffer circuit 322 divides the current change di / dt into a voltage and inputs it as a voltage. The output V'out of the buffer circuit 322 is a force f (contact force with the target object). The buffer circuit 322 is, for example, a voltage follower circuit, and is configured such that the current change di / dt is converted into a voltage and input to the positive input terminal, and the negative input terminal and output terminal are connected. The buffer circuit 322 may have an oscillation-preventing resistor or capacitor connected to its output terminal, for example.

[0099] The differential amplifier circuit 321 receives the change in current flowing across the inductance L and outputs an output Vout, which is a force differential value, to the control unit 33 A. The value of the inductance L and the gain α of the differential amplifier circuit 321 are determined by experiment or simulation depending on, for example, the characteristics of the sensor, the target object, the work content, etc.

[0100] According to this circuit configuration, in addition to the force differential output Vout=-αLdi / dt of the circuit configuration of FIG. 6, the force f can also be output from the control unit 33A. The control unit 33A may use this force f to offset the force command or increase or decrease the gain. Note that the control unit 33A may perform both the offset of the force command and the increase or decrease of the gain, or may perform only one of them.

[0101] As a result, in this modified example, the time change value of the force can be directly measured and generated by an analog circuit using the inductance L of the time change output circuit 32. And, according to this modified example, since the circuit configuration is an analog circuit, responsiveness is high. Furthermore, with the modified circuit configuration, there is no need for a circuit that stores or reads the previous value of the force as in the example described above, and therefore it can be made smaller.

[0102] [Processing Procedure] Next, an example of a processing procedure of the control system 1 using the force differential value of this embodiment will be described. Fig. 19 is a flowchart of the processing of the control system according to this embodiment. Note that the processing procedure using Fig. 19 will explain the processing in the case of the circuit configuration of Fig. 6. In the case of the circuit configuration of Fig. 18, for example, the force is also detected in step S3, and the force command is offset and the gain is increased or decreased in step S4.

[0103] (Step S1 ) The acquisition unit 31 acquires a detection value from the sensor 23 of the hand 2 .

[0104] (Step S2) The time variation output circuit 32 extracts a contact point using the acquired detection value, and determines the position of the extracted contact point.

[0105] (Step S3) The time change output circuit 32 receives the detection value acquired by the acquisition unit 31 as an input and generates a force differential value, which is a time change value of the force.

[0106] (Step S4) The control unit 33 generates a control value for controlling the hand 2 using the force differential value output by the time change output circuit 32.

[0107] (Step S5) The output unit 35 outputs the generated control value to the hand 2. As a result, the control device 3 applies force to the contact surface with the multiple fingers 21 (movable part), thereby controlling the movable part or the contact object.

[0108] In the above-described embodiments, examples have been described in which a robot hand or the like grasps a target object without slipping, but the present invention is not limited to this. The control method of each of the above-described embodiments can be applied to machines and devices that are intended to suppress slippage, such as saddle-type vehicles, motorcycles, three-wheeled vehicles, four-wheeled vehicles, automatic lawnmowers, tillers, snowplows, and devices that assist human movement, in addition to robot hands or the like.

[0109] A program for implementing all or part of the functions of the control device 3 of the present invention may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be loaded into a computer system and executed to perform all or part of the processing performed by the control device 3. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. The term "computer system" also includes a WWW system equipped with a homepage provision environment (or display environment). The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. The term "computer-readable recording medium" also includes devices that retain a program for a certain period of time, such as volatile memory (RAM) within a computer system that acts as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. Alternatively, some or all of these components may be realized by LSI (Large Scale Integration) hardware (including circuitry) such as an ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), GPU (Graphics Processing Unit), or SOC (System On Chip), or may be realized by a combination of software and hardware.

[0110] The program may also be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may also be a program that realizes part of the above-mentioned functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0111] The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment, and various modifications and substitutions can be made within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0112] 1...control system, 2...hand, 3...control device, 21, 21-1,..., 21-n...finger portion, 22, 22-1,..., 22-n...actuator, 23, 23-1,..., 23-n...sensor, 24...base portion, 31...acquisition portion, 32, 32A...time change output circuit, 33, 33A...control portion, 34...drive circuit, 35...output portion, 36...storage portion

Claims

1. a differential amplifier circuit that receives a value obtained by a sensor that acquires a contact force with a target object and a current change value due to inductance in the sensor value, and outputs a time change value of the contact force with the target object; A time-varying output circuit comprising:

2. One end of the sensor is connected to a power supply voltage; one end of the inductance is connected to the other end of the sensor and the positive input terminal of the differential amplifier circuit, and the other end is connected to the negative input terminal of the differential amplifier circuit and is also grounded; the differential amplifier circuit outputs a time change value of force obtained by multiplying a difference between a value input to the positive input terminal and a current change value input to the negative input terminal by a gain of the differential amplifier circuit.

2. The time-varying output circuit of claim 1.

3. a resistor and a buffer circuit, An input of a current change value due to the inductance of the sensor value is grounded via the resistor and connected to an input of a buffer circuit; the buffer circuit outputs the contact force with the target object.

2. The time-varying output circuit of claim 1.

4. One end of the sensor is connected to a power supply voltage; one end of the inductance is connected to the other end of the sensor and the positive input terminal of the differential amplifier circuit, and the other end is connected to the negative input terminal of the differential amplifier circuit, one end of the resistor, and the first input terminal of the buffer circuit; The other end of the resistor is grounded, the differential amplifier circuit outputs a time change value of force obtained by multiplying a difference between a value input to the positive input terminal and a current change value input to the negative input terminal by a gain of the differential amplifier circuit. The buffer circuit has two input terminals connected to an output terminal, and outputs the contact force with the target object.

4. The time varying output circuit of claim 3.

5. The sensor is a sensor whose resistance changes in response to an applied force.

3. The time-varying output circuit according to claim 1 or 2.

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