Movable body control method and movable body control device

Abstract

To provide a movable body control method and a movable body control device capable of easily suppressing and stabilizing a slip by using a force sensor without identifying or estimating a physical parameter.SOLUTION: A movable body control method is a method of controlling a contact object or a movable portion itself by at least one movable portion and the contact object in contact with the movable portion, in which a control device controls the movable portion or the contact object by applying force to a contact surface by a plurality of movable portions, and in which when contact force generated on the contact surface is calculated based on energy, total energy in the entire movable portion or the contact object is a sum of stored energy and attenuated energy and is not increased; an external force term in a term of the stored energy includes information of sliding with respect to the contact surface between the movable portion and the contact object; and the external force term is calculated to be integrable.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a movable body and a device for controlling a movable body. [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 the 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. 5829103 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the prior art, control of the sliding contact state required estimating the slip parameters and completing the physical parameters of the controlled object, which was a difficult task. Thus, in the prior art, it was necessary to estimate the slip using some kind of estimator, which was difficult.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a movable body control method and a movable body control device that can easily suppress and stabilize slippage using a force sensor without identifying or estimating physical parameters. [Means for solving the problem]

[0008] (1) In order to achieve the above object, a movable body control method according to one aspect of the present invention is a method for controlling a contacting object (e.g., a target object in the case of a finger) or the movable body itself (e.g., the bike itself in the case of a bike) using at least one movable part (e.g., a finger or a bike) and a contacting object (e.g., a grasped object or a floor surface) that comes into contact with the movable part, in which a control device controls the movable part or the contacting object by applying force to the contact surface using multiple movable parts, and when calculating the contact force generated on the contact surface based on energy, the total energy of the entire movable part or the contacting object is considered to be the sum of stored energy and damping energy and does not increase, and the external force term in the stored energy term includes information on the sliding of the movable part and the contacting object relative to the contact surface, and is calculated so that the external force term is integrable.

[0009] (2) In order to achieve the above object, a movable body control method according to one aspect of the present invention is a control method for manipulating a contact object using a hand having a plurality of finger portions, wherein the finger portions are movable portions, a control device controls the position and posture of the contact object by applying force using the plurality of finger portions, and when calculating the contact force generated on the contact surface between the finger portions and the contact object based on energy, the energy of the entire movable portion is the sum of stored energy and damping energy and does not increase, and an external force term in the stored energy term includes information on slippage on the contact surface between the finger portions and the contact object, and is calculated so that the external force term is integrable.

[0010] (3) In the movable body control method according to the aspect of the present invention described above in (1) or (2), the external force term is a sum of time-differentiated contact forces of the movable parts with respect to the contact object, expressed by the following equation:

[0011]

number

[0012] f is the force at the contact point, and p · may be the change in position of the contact point.

[0013] (4) In the movable body control method according to any one of (1) to (3) above, a command value of a time derivative of energy of the movable part is expressed by the following equation:

[0014]

number

[0015] k f may be the gain and f the force at the contact point.

[0016] (5) In the movable body control method according to the above (1) or (2) aspect of the present invention, the control device · cmdBy offsetting using the following equation, the change in slip is extracted and controlled.

[0017]

number

[0018] f cmd is the target force value, and f act may be slippage information.

[0019] (6) In the movable body control method according to the aspect of the present invention described above in (1) or (2), the control device calculates a force command E to the movable part that is correlated with a Lyapunov function using the following equation: · cmd The gain is increased or decreased based on the change in

[0020]

number

[0021] k f , k e Each of them may be a gain.

[0022] (7) In order to achieve the above object, a control device for a movable body according to one embodiment of the present invention is a control device for a movable body that controls at least one movable part and a contacting object that comes into contact with the movable part, or the movable part itself (in the case of a motorcycle, the motorcycle itself), and is equipped with a control command generation unit that controls the movable part or the contacting object by applying force to the contact surface using multiple movable parts, and a contact force calculation unit that, when calculating the contact force generated on the contact surface based on energy, calculates the contact force by assuming that the total energy of the entire movable part or the contacting object is the sum of stored energy and damping energy and does not increase, and the contact force calculation unit is a control device for a movable body that calculates an external force term in the stored energy term that includes information on the sliding of the movable part and the contacting object relative to the contact surface, and that the external force term is integrable.

[0023] (8) In order to achieve the above object, a control device for a movable body according to one embodiment of the present invention is a control device that operates a contact object using a hand with a plurality of finger portions, and includes: a control command generation unit that controls the position and posture of the contact object by applying force using the plurality of finger portions; a contact force calculation unit that, when calculating the contact force generated on the contact surface between the finger portions and the contact object based on energy, calculates the contact force by assuming that the energy of the entire movable portion is the sum of stored energy and damping energy and does not increase; and an external force term in the stored energy term of the contact force calculation unit includes information on slippage on the contact surface between the finger portions and the contact object, and calculates the external force term so that it is integrable. [Effects of the Invention]

[0024] According to the above (1) to (8), slippage can be easily suppressed and stabilized using a force sensor without identifying or estimating physical parameters. [Brief explanation of the drawings]

[0025] [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 hand 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. 4 is a diagram illustrating an example of the relationship between each gripping energy and position in the first embodiment. [Figure 7] 1 is a diagram illustrating an example of the configuration of a control system according to a first embodiment. [Figure 8] FIG. 10 is a side view of the hand during gripping. [Figure 9]This is an example of grasping operation using point contact and rolling contact in the conventional method. Figure 9 shows the simulation results. [Figure 10] 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 11] 10 shows an example of a gripping operation using point contact, rolling contact, and sliding contact in the first embodiment. [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 gripping operation with point contact, rolling contact, and sliding contact in the first embodiment. [Figure 13] 10A and 10B are diagrams showing examples of changes in actual acceleration, actual force, and actual Power with respect to time during control by a conventional method and during control by the first embodiment. [Figure 14] 4 is a flowchart of a process of a control system according to an embodiment. [Figure 15] FIG. 1 is a diagram for explaining problems with the prior art. [Figure 16] 10A and 10B are diagrams illustrating examples of gripping states under control in which a force command is offset and a gain is increased or decreased in an embodiment. [Figure 17] FIG. 10 is a diagram showing an example of a simulation result when control is performed using a conventional technique and when control is performed using a first technique of the present embodiment. [Figure 18] 10A and 10B are diagrams showing examples of simulation results when control is performed using a conventional technique and when control is performed using a second technique of the present embodiment. [Figure 19] 10 is a flowchart of processing in a control system according to a second embodiment. [Figure 20] 10 is a flowchart of processing in a control system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] 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).

[0027] [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 (contact 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.

[0028] 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.

[0029] 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.

[0030] The hand 2 may be remotely controlled 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 2 and the target object, or the hand 2 may be controlled automatically.

[0031] 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 points of contact. 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.

[0032] Note that the gripping unit in this embodiment is controlled without using images captured by the imaging device. Also, in this embodiment, grip stabilization control can be performed without using the coefficient of friction between the target object obj and the fingers, etc.

[0033] First Embodiment 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

[0034]

number

[0035] 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

[0036]

number

[0037] 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.

[0038] 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

[0039]

number

[0040] 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 the formula is the following formula (4). In this embodiment, formula (4) is defined as "f tip " and "f" and simplified to "p · tip " to "p · " and simplify it to E add =∫(f p · )dt. This allows us to implicitly understand the shape of the potential function and achieve Lyapunov stability.

[0041]

number

[0042] 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. 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).

[0043]

number

[0044] Equation (5) is add =∫(f p · )dt, equation (4) can also be expressed as the following equation (6).

[0045]

number

[0046] 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.

[0047] [Unknown object stabilization grasping method] Next, an example of a method for including slip information in the external force term will be described. FIG. 6 is a diagram showing an example of the relationship between each energy level and position in the gripping state in this embodiment. The horizontal axis represents position, and the vertical axis represents energy. Each line represents the energy level versus position. all , E kinetic , E potential , and E add is.

[0048] As shown in Figure 6, E all and E potential and E add curves upwards towards the center position, and E kinetic curves downwards towards the center. all is known, and E kinetic is unknown, and E potential is unknown, and E add is partially known. The Lyapunov function is the potential E potential , and E add Therefore, E potential , and E add If the sum of E and E is not convex downward, it will not be stable. add Increase the gain of (E add (Only modify the curve) so that it is convex downward.

[0049] Here, assuming E add If is based on potential, then Eadd The change in E potential changes at the same time. E add If is based on potential, for example, E add = h(x) (x is the position) and E add is E potential It becomes an upward convex curve according to the Suppose E add If is based on kinetics, then E add The change in E kineticと change at the same time. E add If is based on kinetics, E add is E kinetic It forms a downward convex curve.

[0050] In this way, at least, we can see the shape of Eadd. AllPotential is expressed as the following equation (7).

[0051]

number

[0052] Also, the potential function E AllPotential is required to satisfy the following equation (8), E add is required to be the following equation (9).

[0053]

number

[0054]

number

[0055] In this way, E add By observing the change in , we can know whether equation (8) is negative. Note that this precondition is based on the total energy E all is a conservative system.

[0056] The control device 3 controls the movable parts or the contacting object by applying a force to the contact surface using multiple movable parts (e.g., fingers 21). When calculating the contact force acting on the contact surface based on energy, the control device 3 assumes that the total energy of the entire movable parts or the contacting object is the sum of stored energy and damping energy, and does not increase. The control device 3 calculates the external force term in the stored energy term so that it includes information about slippage between the movable parts and the contacting object on the contact surface and is integrable.

[0057] [Control system configuration example] Next, an example of the configuration of the control system of this embodiment will be described. 7 is a diagram showing an example of the configuration of a control system according to this embodiment. 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 contact force calculation unit 32, a control value generation unit 33, a drive circuit , an output unit 35, and a storage unit .

[0058] 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.

[0059] The fingers 21 (21-1, . . . , 21-n) have joints.

[0060] 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 .

[0061] 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).

[0062] The base 24 is the part to which the fingers 21 are attached.

[0063] 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.

[0064] The acquisition unit 31 acquires the detection information detected by the sensor 23 of the hand 2 .

[0065] The contact force calculation unit 32 calculates the contact force so that the external force term in the conserved energy term includes information about the slippage between the finger 21 and the contact surface of the contact object, as in the above-mentioned equation, and the external force term is integrable.

[0066] The control value generation unit 33 generates a control value for the hand 2 using the contact force calculated by the contact force calculation unit 32. If the control device 3 includes a drive circuit 34, the control value generation unit 33 outputs the generated control value to the drive circuit 34. If the hand 2 includes a drive circuit 34, the control value generation unit 33 outputs the generated control value to the output unit 35.

[0067] 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 value generation unit 33. The drive circuit 34 may be provided in the hand 2.

[0068] When the control device 3 includes a drive circuit 34, the output unit 35 outputs the control value generated by the control value generation 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.

[0069] The storage unit 36 ​​stores programs, thresholds, mathematical expressions, identification information for identifying the hand 2, and the like, which are necessary for control.

[0070] 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.

[0071] [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. 8 is a side view of the hand during grasping. The example in Fig. 8 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.

[0072] 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.

[0073] 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 (10). ref and p act Each of these is a fixed value. In equation (10), 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 by the following equation (11).

[0074]

number

[0075]

number

[0076] FIG. 9 shows an example of a grasping operation using point contact and rolling contact according to a conventional method. Note that FIG. 9 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 force and each axis generated in each finger 21 of reference symbol 201. Reference symbol 212 indicates the force and each axis generated in each finger 21 of reference symbol 202. Reference symbol 213 indicates the force and each axis 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.

[0077] Figure 10 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 10 is a simulation result. The horizontal axis of 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 8. The horizontal axis of symbol g240 is time (sec), and the vertical axis is the velocity (m / s) generated at the contact point.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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).

[0082] FIG. 11 shows an example of a grasping operation using point contact, rolling contact, and sliding contact according to this embodiment. Note that FIG. 11 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.

[0083] Figure 12 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 12 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 13 is a diagram showing an example of changes in actual acceleration, actual force, and actual Power with respect to time when controlled by a conventional method and when controlled by this embodiment. Note that FIG. 13 shows only the z direction of the contact point.

[0089] Graph g400 shows the change in actual acceleration over time, with the horizontal axis representing time (sec) and the vertical axis representing actual acceleration (m / s). Line g401 represents control using the conventional method, and line g402 represents control using this embodiment. Graph g410 shows the change in actual acceleration over time, with the horizontal axis representing time (sec) and the vertical axis representing actual force (N). Line g411 represents the case of control using the conventional method, and line g412 represents the case of control using this embodiment.

[0090] As shown in graphs g400 and g410, when controlled using the conventional method, slip occurs as indicated by arrow g403, and then the target object is dropped as indicated by arrow g404. In contrast to this, during control in this embodiment, even after slippage occurs as indicated by arrow g405, the target object is not dropped and is maintained in grip (Keep) as indicated by arrow g406.

[0091] Graph g420 shows the change in actual power (J / s) over time, with the horizontal axis representing time (sec) and the vertical axis representing actual power (J / s). Line g421 represents the change in command power E · cmd , line g422 is the actual power of control (Actual Power) E · act In addition, the actual power E · act The vertical axis is shown at 500x magnification. The meaning of the movement of the force during control in this embodiment is that, as shown in graph g420, the finger 21 moves and tries to do work in the upward direction of the z-axis (actual power E · act ) to the negative power correction (Command Power E · cmd ) is inserted to return it.

[0092] As a result, according to the control method of this embodiment, a camera is not used, but rather the detection value of the sensor is used to issue an appropriate grasping command (internal force), and stable grasping is possible even if the target object obj unintentionally slips off the finger portion 21. Furthermore, according to this embodiment, slippage can be easily suppressed and stabilized using a sensor that can indirectly or directly measure the time derivative of force without identifying or estimating physical parameters.

[0093] [Example of processing procedure] Next, an example of a processing procedure of the control system 1 of this embodiment will be described. FIG. 14 is a flowchart of the processing of the control system according to this embodiment.

[0094] (Step S1) The acquisition unit 31 acquires a detection value from the sensor 23 of the hand 2.

[0095] (Step S2) The contact force calculation unit 32 extracts a contact point using the acquired detection value, and determines the position of the extracted contact point.

[0096] (Step S3) The contact force calculation unit 32 calculates the contact force at the determined contact point, including an external force term. When calculating the contact force acting on the contact surface based on energy, the contact force calculation unit 32 assumes that the total energy of the entire finger 21 or the contacting object is the sum of stored energy and damping energy, and does not increase. The contact force calculation unit 32 calculates the external force term in the stored energy term so that it includes information about the sliding between the finger 21 and the contacting object on the contact surface and the force term is integrable.

[0097] (Step S4) The control value generation unit 33 generates a control value for controlling the hand 2 using the calculated contact force at the contact point.

[0098] (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.

[0099] [Second embodiment] Next, a further improvement of the above-described embodiment will be described. Fig. 15 is a diagram for explaining the problems of the conventional technology. As shown in Fig. 15, for example, a target object placed on a desk is picked up and grasped with two fingers. The target object obj is an image of an object such as a small, irregularly shaped rock. Reference symbol g501 indicates how the target object obj is grasped by the hand 2. In the example of Fig. 15, the hand 2 includes three or more fingers 21, for example. Reference symbols g511 to g513 indicate states in which the finger portions 21 begin to grasp the target object obj from the left and right, apply force from the left and right, and then fail and drop it as shown by reference symbol g513. Note that in reference symbols g511 to g513, each line indicates an axial direction, a force acting from the fingertip to the target object, etc.

[0100] Symbol g520 is the relationship of the Lyapunov function to the command force. 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.

[0101] 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.

[0102] 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 in the following equation (12). · cmd is the above-mentioned E add Corresponds to.

[0103]

number

[0104] And the target force instruction f cmd is expressed as in the following equation (13): In equation (13), PI represents PI (Proportional-Integral) control.

[0105]

number

[0106] In contrast to this, in this embodiment, in order to extract the change during slippage, the control value generator 33 offsets the force command as shown in the following equations (14) and (15). In this way, in this embodiment, since the error component is subtracted, only the change during slippage can be extracted and controlled.

[0107]

number

[0108]

number

[0109] The offset is defined as the target value of the energy change E · cmd f in Eq. (12) act and f · act From this, f is obtained as shown in equation (15). 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 (12), act 15, the curve converges to the minimum value g527 as shown by the line g524 in Fig. 15. On the other hand, in the control of the present embodiment, the curve f cmd From f act By offsetting (drawing) the line g574 can be controlled so that it does not converge at the boundary line like lines g574 and g575 in Figure 16, but rather line g574 becomes the bottom.

[0110] Furthermore, in this embodiment, in order to make the change gentler, the control value generating unit 33 generates 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.

[0111]

number

[0112] 16 is a diagram showing an example of a gripping state obtained by control in which the force command is offset and the gain is increased or decreased in this embodiment. The target object obj is, for example, an image of an object such as a small, irregularly shaped rock. Reference symbols g551 to g554 indicate states in which the finger portions 21 start to grasp the target object obj from the left and right, and continue to grasp it without dropping it even when force is applied from the left and right, as shown by reference symbol g554. Note that in reference symbols g551 to g554, each line indicates an axial direction, a force acting from the fingertip to the target object, etc. Symbol g570 is the relationship of the Lyapunov function to the command force. 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.

[0113] In the control of this embodiment, when the boundary between the static friction region and the dynamic friction region is crossed, the change is controlled gradually as indicated by the arrow g576, making it possible to continue grasping, for example, as indicated by the symbol g554. As a result, even at the boundary position, the change is gradual as indicated by the arrow g576, rather than a minimum value represented by a steeply inclined line as in FIG. 15. In this embodiment, control is performed to remain in the static friction region where a stable grasp can be maintained. In this embodiment, such control solves the problems of the prior art.

[0114] Furthermore, examples of simulation results for the case where the object is grasped using only the first method of this embodiment and the case where the object is grasped using only the second method will be described. Note that the first method is the case where the object is grasped using the force conversion (=f cmd The second method is the method of dynamically adjusting the gain k as described above.

[0115] 17 is a diagram showing example simulation results for control using a conventional technique and control using the first technique of this embodiment. The target object obj is an image of an object such as a truncated pyramid. In the images marked with symbols g600, g611, g612, g621, and g622, each line indicates the axial direction, the force acting from the fingertip to the target object, etc.

[0116] The image g600 is an example of the state at the start of control. Images g611 and g612 are examples of a state where the force change is offset and controlled using the conventional technique. As in the image g612, when a quadrangular pyramidal object is grasped, the conventional technique is unable to hold the target object and causes it to drop. The images g621 and g622 are examples of a state where the force change is offset and controlled using the first method. On the other hand, even when a quadrangular pyramidal object is grasped, as in the image g622, the target object can be held without dropping using only the first method of this embodiment.

[0117] 18 is a diagram showing example simulation results for control using a conventional technique and control using the second technique of this embodiment. The target object obj is an image of an object such as a truncated pyramid. In the images marked with symbols g650, g661, g662, g671, and g672, each line indicates the axial direction, the force acting from the fingertip to the target object, etc.

[0118] The image with reference numeral g650 is an example of the state at the start of control. The images g661 and g662 are examples of a state in which the gain is dynamically adjusted and controlled using the conventional technique. As can be seen from the images g661 and g662, with the conventional technique, the target object sways violently from side to side and up and down, making it impossible to hold and causing it to fall. The images with symbols g671 and g672 are examples of a state in which the gain is dynamically adjusted and controlled using the second method. On the other hand, as shown in the images with symbols g671 and g672, even using only the second method of this embodiment, the target object shakes less and can be held without falling.

[0119] In the example described with reference to FIGS. 15 to 18, the example is described in which the object is gripped with two fingers, but the number of fingers used for gripping may be three or more. Moreover, the method of the second embodiment and the method of the third embodiment described above may be used alone or in combination.

[0120] [Example of processing procedure] Next, an example of the processing procedure of the control system 1 in each of the second and third embodiments will be described. FIG. 19 is a flowchart of the process of the control system according to the second embodiment.

[0121] (Step S11) The acquisition unit 31 acquires a detection value from the sensor 23 of the hand 2.

[0122] (Step S12) The contact force calculation unit 32 extracts a contact point using the acquired detection value, and determines the position of the extracted contact point.

[0123] (Step S13) The contact force calculation unit 32 calculates the contact force at the obtained contact point, including an external force term.

[0124] (Step S14) The contact force calculation unit 32 offsets the force instruction using the above-mentioned equations (14) and (15).

[0125] (Step S15) The control value generating unit 33 generates a control value for controlling the hand 2 using the offset force instruction.

[0126] (Step S16) The output unit 35 outputs the generated control value to the hand 2.

[0127] FIG. 20 is a flowchart of the process of the control system according to the third embodiment.

[0128] (Step S21) The acquisition unit 31 acquires a detection value from the sensor 23 of the hand 2.

[0129] (Step S22) The contact force calculation unit 32 extracts a contact point using the acquired detection value, and determines the position of the extracted contact point.

[0130] (Step S23) The contact force calculation unit 32 calculates the contact force at the obtained contact point, including an external force term.

[0131] (Step S24) The contact force calculation unit 32 increases or decreases the gain using the above-mentioned equation (16).

[0132] (Step S25) The control value generating unit 33 generates a control value for controlling the hand 2 using the increased or decreased gain.

[0133] (Step S26) The output unit 35 outputs the generated control value to the hand 2.

[0134] As described above, in each embodiment, the external force term E add The slip information is included in the external force term E add is made integrable (the system is a conservative system). As a result, in this embodiment, the shape of the potential function is implicitly known and Lyapunov stability is achieved.

[0135] As a result, according to each embodiment, slip suppression and stabilization can be achieved simply and easily by using the detection values ​​of a sensor that can indirectly or directly measure the time derivative of force, without identifying or estimating physical parameters.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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]

[0140] 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... contact force calculation portion, 33... control value generation portion, 34... drive circuit, 35... output portion, 36... storage portion

Claims

1. A method for controlling at least one moving part and a contact object that comes into contact with the moving part, the contact object or the moving part itself (in the case of a motorcycle, the motorcycle itself), The control device a plurality of the movable parts applying a force to a contact surface to control the movable parts or the contact object; When calculating the contact force generated on the contact surface based on energy, the total energy of the entire movable part or the contact object is the sum of stored energy and damped energy and does not increase, an external force term in the term of the stored energy includes information on slippage between the movable part and the contact object relative to the contact surface, and is calculated so that the external force term is integrable; A method for controlling a moving object.

2. A control method for manipulating a contact object with a hand having a plurality of finger portions, comprising: the finger is a movable part, The control device a plurality of finger portions applying a force to control the position and posture of the contact object; When calculating the contact force generated on the contact surface between the finger portion and the contact object based on energy, the energy of the entire movable portion is the sum of stored energy and damped energy and does not increase, an external force term in the term of the stored energy includes information on slippage between the finger and the contact object on the contact surface, and is calculated so that the external force term is integrable; A method for controlling a moving object.

3. The external force term is the sum of the contact forces of the respective movable parts with respect to the contact object, which are differentiated with respect to time, and is expressed by the following equation: [Equation 1] f is the force at the contact point, and p ・ is the change in position of the contact point, The movable body control method according to claim 1 or 2.

4. A command value of the time derivative of the energy of the movable part is expressed by the following equation: [Equation 2] k ｆ is the gain and f is the force at the contact point. The movable body control method according to claim 1 or 2.

5. The control device The force command E to the movable part ・ ｃｍｄ By offsetting using the following equation, the change in slip is extracted and controlled. [Equation 3] f ｃｍｄ is the target force value, and f ａｃｔ is the slippage information, The movable body control method according to claim 1 or 2.

6. The control device Using the following equation, the force command E to the moving part, which is correlated with the Lyapunov function, ・ ｃｍｄ The gain is increased or decreased based on the change in [Equation 4] k ｆ , k ｅ Each is a gain, The movable body control method according to claim 1 or 2.

7. A control device for a movable body that controls at least one movable part and a contact object that comes into contact with the movable part, and controls the contact object or the movable part itself (the motorcycle itself in the case of a motorcycle), a control command generation unit that controls the movable units or the contact object by applying a force to a contact surface by the plurality of movable units; a contact force calculation unit that calculates the contact force generated on the contact surface based on energy, assuming that the total energy of the entire movable part or the contact object is the sum of stored energy and damped energy and does not increase; Equipped with the contact force calculation unit calculates an external force term in the stored energy term such that the external force term includes information on slippage between the movable part and the contact object relative to the contact surface, and the external force term is integrable. Control device for moving objects.

8. A control device for operating a contact object by a hand having a plurality of finger portions, a control command generation unit that controls the position and posture of the contact object by applying forces using the plurality of finger units; a contact force calculation unit that calculates the contact force generated on the contact surface between the finger unit and the contact object based on energy, assuming that the energy of the entire movable unit is the sum of stored energy and damped energy and does not increase; the contact force calculation unit calculates an external force term in the stored energy term such that the external force term includes information on slippage between the finger and the contact object on the contact surface, and the external force term is integrable. Control device for moving objects.

Images