JP2014121761A - Linkage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linkage capable of setting the rigidity of an elastic element of a joint mechanism in an appropriate range in order to prevent the joint mechanism from being damaged because of collision of a movable part with an external object.SOLUTION: A linkage 1 is constituted so that the rigidity k_i of an elastic element 5 of each joint mechanism Ji can be changed in the range higher than first rigidity k1_i and lower than second rigidity k2_i. The first rigidity k1_i is set so that joint maximum elastic energy becomes higher than joint minimum inertial collision kinetic energy. The second rigidity k2_i is set so that a third time becomes longer than a fourth time.

Description

  The present invention includes one or a plurality of joint mechanisms provided between a base and a movable portion movable with respect to the base, and an actuator that outputs a driving force that displaces the one or more joint mechanisms. And each of the one or more joint mechanisms relates to a link mechanism configured to transmit power via an elastically deformable elastic element configured to be capable of variably controlling rigidity.

  Conventionally, a plurality of joint mechanisms provided between a base body and a movable part movable with respect to the base body, and an actuator that outputs a driving force for displacing the plurality of joint mechanisms, each of the plurality of joint mechanisms is A link mechanism configured to transmit power via an elastically deformable elastic element configured to be capable of variably controlling rigidity is known (Patent Document 1). In this link mechanism, when the movable part collides with an external object, the rigidity of the elastic element of the joint mechanism is controlled to be a predetermined rigidity.

JP 2008-30296 A

  In the link mechanism as described in Patent Document 1, it is conceivable to change the rigidity of the elastic element of the joint mechanism in order to prevent the joint mechanism from being damaged when the movable part collides with the object. .

  However, conventionally, in order to prevent damage to the joint mechanism, an appropriate setting range of the rigidity of the elastic element of the joint mechanism has not been sufficiently studied. Therefore, it has been necessary to set an appropriate setting range of the stiffness of the elastic element of the joint mechanism after trial and error, or to set a range with a sufficient margin, that is, an excessively wide range.

  The present invention has been made in view of the above points, and includes one or a plurality of joint mechanisms provided between a base and a movable portion movable with respect to the base, and one or a plurality of joint mechanisms. Each of the one or more joint mechanisms is configured to transmit power via an elastically deformable elastic element configured to variably control rigidity. Provided is a link mechanism that can set the rigidity of an elastic element of an articulation mechanism within an appropriate range in order to prevent the articulation mechanism from being damaged when a movable part collides with an external object. For the purpose.

  The present invention includes one or a plurality of joint mechanisms provided between a base and a movable portion movable with respect to the base, and an actuator that outputs a driving force that displaces the one or more joint mechanisms. Each of the one or more joint mechanisms is a link mechanism configured to transmit power via an elastically deformable elastic element configured to be variably controllable in rigidity, The rigidity of the elastic element of each of the one or more joint mechanisms can be changed within a range of a first rigidity or more and a second rigidity or less set for each of the one or more joint mechanisms. In each of the one or more joint mechanisms, the first rigidity of the elastic element of the joint mechanism is such that the amount of elastic deformation of the elastic element of the joint mechanism is the amount of elastic deformation of the elastic element of the joint mechanism. In case of maximum deformation When the elastic energy of the elastic element of the joint mechanism is displaced, the moment of inertia or the inertial mass of the joint mechanism is a minimum value that can be taken by the joint mechanism, and the elastic energy of the joint mechanism is displaced by the actuator. The joint mechanism is set to be equal to or higher than the kinetic energy of the joint mechanism when it is assumed that the joint mechanism is displaced at the maximum displacement speed that can be realized. In each of the one or more joint mechanisms, the joint mechanism When the joint mechanism is displaced, the second stiffness of the elastic element is such that the moment of inertia or mass of the joint mechanism is a maximum value that the joint mechanism can take, and the displacement of the joint mechanism is started. From the elastic energy of the elastic element of the joint mechanism accumulated by the displacement of the joint mechanism Assuming that the joint mechanism is displaced at the maximum acceleration that can be realized by the actuator, the displacement speed of the joint mechanism is the maximum displacement of the joint mechanism. It is characterized in that it is set to be longer than the time required for changing only the speed.

  Here, the amount of elastic deformation of the elastic element in the present invention means the relative amount of displacement between the side transmitting power to the elastic element and the side transmitting the power via the elastic element. Further, the inertia moment or inertia mass of the joint mechanism when the joint mechanism is displaced is the inertia moment when the joint mechanism is a rotary joint mechanism, and the inertia mass when the joint mechanism is a linear motion joint mechanism.

  Further, when the joint mechanism is displaced, the moment of inertia or the inertial mass of the joint mechanism changes in accordance with the displacement of each of the one or more joint mechanisms (hereinafter referred to as “link mechanism posture”). The maximum value or the minimum value of the moment of inertia or the inertial mass of the joint mechanism is the maximum value or the minimum value that can be taken within the range of postures that can be realized by the link mechanism.

  According to various studies by the inventors of the present application, in order to prevent each joint mechanism from being damaged when the movable part collides with an external object, the elasticity of each joint mechanism is satisfied so as to satisfy the following two conditions. It is necessary to be able to control the stiffness of the element.

(Condition 1)
In each of one or a plurality of joint mechanisms, the kinetic energy (hereinafter referred to as “collision kinetic energy”) due to the displacement of the joint mechanism caused by the collision of the movable part with the object is represented by the elasticity of the elastic element of the joint mechanism. The condition that everything can be converted into energy.

(Condition 2)
In each of the one or more joint mechanisms, the elastic elements of the joint mechanism accumulated by the displacement of the joint mechanism from the time when the displacement of the joint mechanism due to the collision of the movable part with the object is started. The time until the displacement of the joint mechanism due to elastic energy, in other words, the time during which the elastic element of the joint mechanism absorbs the impact (hereinafter referred to as “first time”) is determined by the actuator. When the joint mechanism is displaced at the maximum acceleration that the joint mechanism can realize, the displacement speed of the joint mechanism can be changed by a speed obtained by reversing the direction of the relative displacement speed of the joint mechanism due to the collision ( (Hereinafter referred to as “second time”).

  In each of one or a plurality of joint mechanisms, when the above two conditions are satisfied, the impact on the joint mechanism due to the collision of the movable part with the object is absorbed by the elastic element of the joint mechanism. In addition, while the elastic element of the joint mechanism absorbs the impact, the displacement speed of the joint mechanism is reversed and the direction of the relative displacement speed of the joint mechanism due to the collision is reversed. It becomes possible to change only the speed which made it, and it can prevent that the said joint mechanism is forcedly displaced by the elastic energy of the elastic element of the said joint mechanism (effect by Condition 2). By satisfying the above two conditions, the above-described effect can be obtained, so that the joint mechanism can be prevented from being damaged by the collision of the movable part with the object.

  In the present invention, in order to satisfy the above conditions 1 and 2, the following configuration is adopted.

  First, in order to satisfy the above condition 1, the following configuration is adopted. That is, in each of the one or more joint mechanisms, the elastic energy of the elastic element of the joint mechanism when the elastic deformation amount of the elastic element of the joint mechanism is the maximum deformation amount of the elastic element of the joint mechanism is When the joint mechanism is displaced, the moment of inertia or the inertial mass of the joint mechanism becomes the minimum value that can be taken by the joint mechanism, and when the joint mechanism is displaced by the actuator, the joint mechanism has the maximum displacement speed that can be realized. The first stiffness is set so as to be equal to or higher than the kinetic energy of the joint mechanism (hereinafter referred to as “joint minimum inertial collision kinetic energy”).

  The collision kinetic energy increases as the moment of inertia or mass of the joint mechanism increases when the joint mechanism is displaced. The joint minimum inertial collision kinetic energy is the collision kinetic energy when the moment of inertia or the inertial mass of the joint mechanism is the minimum value that the joint mechanism can take when the joint mechanism is displaced. Therefore, under the condition that the rigidity of the elastic element of the joint mechanism and the displacement speed of the joint mechanism are constant, the joint minimum inertial collision kinetic energy is the minimum value that can be taken by the collision kinetic energy.

  By setting the rigidity of the elastic element of the joint mechanism to be equal to or higher than the first rigidity, the inertia moment or the inertial mass of the joint mechanism is any value that the joint mechanism can take when the joint mechanism is displaced. In addition, the stiffness of the elastic element of the joint mechanism can be set so as to satisfy the condition 1 regardless of any value that can be taken when changing the displacement speed of the joint mechanism. .

  In order to satisfy the above condition 2, the following configuration is adopted. That is, in each of one or a plurality of joint mechanisms, when the joint mechanism is displaced, the inertia moment or the inertial mass of the joint mechanism becomes the maximum value that can be taken by the joint mechanism, and the displacement of the joint mechanism is started. The time from the point in time until the point when the displacement of the joint mechanism is started by the elastic energy of the elastic element of the joint mechanism accumulated by the displacement of the joint mechanism (hereinafter referred to as “third time”) is the actuator Assuming that the joint mechanism is displaced at the maximum acceleration that can be realized by the joint mechanism, the time for changing the displacement speed of the joint mechanism by the maximum displacement speed of the joint mechanism (hereinafter referred to as “fourth”). The second rigidity is set so as to be equal to or greater than “time”.

  Here, the first time increases as the moment of inertia or mass of the joint mechanism increases when the joint mechanism is displaced under the condition that the rigidity of the elastic element of the joint mechanism is constant. The third time is the first time when the moment of inertia or inertial mass of the joint mechanism is the maximum value that the joint mechanism can take when the joint mechanism is displaced. Therefore, under the condition that the rigidity of the elastic element of the joint mechanism is constant, the third time is the maximum length that can be taken by the first time.

  The second time increases as the amount of change in the displacement speed of the joint mechanism increases under the condition that the rigidity of the elastic element of the joint mechanism is constant. The fourth time is a second time when the displacement speed of the joint mechanism is changed by the maximum displacement speed of the joint mechanism. Accordingly, under the condition that the rigidity of the elastic element of the joint mechanism is constant, the fourth time is the maximum length that can be taken by the second time.

  Thus, since the second stiffness is set so that the third time, which is the maximum length of the first time, is equal to or greater than the fourth time, which is the maximum length of the second time, the moment of inertia of the joint mechanism Or, even if the inertial mass is any value that the joint mechanism can take, and the value that changes the displacement speed of the joint mechanism is any value that can be taken when changing the joint mechanism, the joint The rigidity of the elastic element of the mechanism can be set to such a rigidity that the first time is equal to or longer than the second time (satisfying condition 2).

  As described above, in each of one or a plurality of joint mechanisms, when the joint mechanism is displaced, the moment of inertia or the inertial mass of the joint mechanism is any value that the joint mechanism can take, and The stiffness of the elastic element of the joint mechanism can be set so as to satisfy the conditions 1 and 2 regardless of the value that can be taken when changing the joint mechanism. In order to prevent the joint mechanism from being damaged when the movable part collides with an external object, the rigidity of the elastic element of the joint mechanism can be set within an appropriate range.

  In the present invention, when any one of the one or more joint mechanisms is defined as the i-th joint mechanism, the first rigidity of the elastic element of the i-th joint mechanism is expressed by the following formula ( It is preferable that it is set to be higher than the rigidity obtained according to 1).

  However, I_min_i indicates the minimum moment of inertia or mass of the i-th joint mechanism that can be taken by the i-th joint mechanism when the i-th joint mechanism is displaced, and ω_max_i indicates the i-th joint mechanism as described above. The maximum displacement speed that can be realized when the actuator is displaced is indicated by x_lim_i, which indicates the maximum deformation amount of the elastic element of the i-th joint mechanism.

  Here, when the rigidity of the elastic element of the i-th joint mechanism is defined as k_i, Expression (1) is k_i that satisfies the following Expression (1-1).

  In Expression (1-1), when the i-th joint mechanism is displaced, the left side indicates that the movable part is an object when the inertia moment or the inertial mass of the i-th joint mechanism is the minimum value that can be taken by the i-th joint mechanism. The kinetic energy of the i-th joint mechanism in the case of colliding with (i.e., the joint minimum inertial collision kinetic energy) is shown. Further, the right side shows the first deformation when the elastic deformation amount of the elastic element of the i-th joint mechanism is the maximum deformation amount of the elastic element of the i-th joint mechanism when the rigidity of the elastic element of the i-th joint mechanism is k_i. The elastic energy of the elastic element of i joint mechanism is shown.

  Accordingly, when the i-th joint mechanism is displaced, the moment of inertia or the inertial mass of the i-th joint mechanism is any value that the i-th joint mechanism can take, and the amount by which the displacement speed of the i-th joint mechanism is changed is The rigidity of the elastic element of the i-th joint mechanism can be set so as to satisfy the above-described condition 1 regardless of any value that can be taken when changing the i-th joint mechanism.

  In the present invention, when any one of the one or more joint mechanisms is defined as the i-th joint mechanism, the second rigidity of the elastic element of the i-th joint mechanism is expressed by the following formula ( It is preferably set to be equal to or less than the rigidity obtained according to 2).

  However, I_max_i indicates the maximum value of the moment of inertia or inertial mass of the i-th joint mechanism that can be taken by the i-th joint mechanism when the i-th joint mechanism is displaced, π indicates the circumference, and A_max_i Indicates the maximum acceleration that can be achieved when the i-th joint mechanism is displaced by the actuator, and ω_max_i indicates the maximum displacement speed that can be achieved when the i-th joint mechanism is displaced by the actuator.

  Here, when the stiffness of the elastic element of the i-th joint mechanism is defined as k_i, equation (2) is k_i that satisfies the following equation (2-1).

  In equation (2-1), the left side indicates that the state of the i-th joint mechanism is the maximum value that can be taken by the i-th joint mechanism when the i-th joint mechanism is displaced. In the state and the stiffness of the elastic element of the i-th joint mechanism is k_i, a quarter cycle of the period represented by the reciprocal of the natural frequency of the elastic element of the i-th joint mechanism is shown. Specifically, the left side of the elastic element of the i-th joint mechanism accumulated by the displacement of the i-th joint mechanism due to the collision from the time when the displacement of the i-th joint mechanism due to the collision of the movable part with the object starts. The time until the time when the displacement of the i-th joint mechanism by elastic energy is started is shown.

  The right side is the maximum acceleration that can be realized by the i-th joint mechanism. When the i-th joint mechanism is displaced by the actuator, the displacement speed of the i-th joint mechanism is realized when the i-th joint mechanism is displaced by the actuator. The time when changing only the maximum possible displacement speed (the shortest time that can be realized by the i-th joint mechanism) is shown.

  Since the time indicated by the left side becomes longer as the rigidity of the elastic element of the i-th joint mechanism is smaller, the i-th joint mechanism is displaced by setting the second rigidity to be equal to or less than the rigidity obtained by the equation (2). When the moment of inertia or the inertial mass of the i-th joint mechanism is any value that the i-th joint mechanism can take, and when the amount of change in the displacement speed of the i-th joint mechanism changes the i-th joint mechanism The rigidity of the elastic element of the i-th joint mechanism can be set so as to satisfy the condition 2 described above regardless of which value can be taken.

  In the present invention, each of the one or more joint mechanisms is configured to transmit power via the elastic element and a viscous element configured to variably control a viscosity coefficient. Alternatively, the viscosity coefficient of the viscous element of each of the plurality of joint mechanisms can be changed within a range of the first viscosity coefficient and the second viscosity coefficient that are set for each of the one or more joint mechanisms. And the first viscosity coefficient of the viscous element of each of the one or more joint mechanisms is assumed to be equal to the joint when the rigidity of the elastic element of the joint mechanism is equal to the first rigidity. A behavior characteristic of the mechanism is set to be a critical damping characteristic or an over-damping characteristic, and the second viscosity coefficient of the viscous element of each of the one or more joint mechanisms is a stiffness of the elastic element of the joint mechanism Is equal to the second stiffness If it is assumed, it is preferable that the behavioral characteristics of the joint mechanism is configured such that the characteristics of critical damping or overdamping.

  Thereby, even if the rigidity of the elastic element of one or a plurality of joint mechanisms is changed to any rigidity within the range of the first rigidity or more and the second rigidity or less, The viscosity coefficient at which the behavior characteristic of the joint mechanism becomes a critical damping characteristic or an excessive damping characteristic is included in the range of the first viscosity coefficient and the second viscosity coefficient.

  Accordingly, it is possible to change the viscosity coefficient of the viscous element of each joint mechanism so that the behavior characteristic of each of the one or more joint mechanisms becomes a critical damping characteristic or an overdamping characteristic. Is prevented from becoming a characteristic of damped vibration. And generation | occurrence | production of the vibration of a movable part according to the damped vibration of each joint mechanism is prevented, and collision with a movable part and an object by the elasticity of the elastic element of each joint mechanism is prevented. Thereby, damage of each joint mechanism by a movable part colliding with an object can be prevented.

The figure which shows the link mechanism of embodiment of this invention. The figure which shows the joint mechanism of the link mechanism of FIG. The figure which shows the transmission mechanism of the joint mechanism of FIG. The figure which shows the characteristic variable mechanism of the transmission mechanism of FIG. VV sectional view taken on the line of FIG.

(1. Configuration)
(1-1. Link mechanism)
With reference to FIGS. 1-5, the link mechanism of embodiment of this invention is demonstrated. As shown in FIG. 1, the link mechanism 1 includes a base body 2, a distal end portion 3, a plurality of joint mechanisms Ji (i = 1, 2,..., N), and a plurality of link members Li (i = 0, 1,..., N) and an actuator 4 (see FIG. 2).

  “I” of the plurality of joint mechanisms Ji represents the order when counting from 1 toward the tip 3 from the base body 2. In addition, when explicitly specifying that the order of the joint mechanism is i-th, it is expressed as the i-th joint mechanism. For example, the j-th joint mechanism may be expressed as “j-th joint mechanism Jj”. Further, “i” of the plurality of link members Li represents the order when counting from 0 toward the tip 3 from the base body 2. In addition, when specifying explicitly that the order of a link member is i-th, it represents with an i-th link member. For example, the jth link member may be represented as “jth link member Lj”.

  The base 2 is fixed at a predetermined position such as on the floor surface. In addition, the base | substrate 2 is equipped with a motive power apparatus etc., and it may be comprised so that the position and attitude | position can be changed with the driving force of this motive power apparatus. The distal end portion 3 functions as an end effector in the link mechanism 1. The tip portion 3 is connected to the base body 2 by a plurality of link members Li that are connected via a plurality of joint mechanisms Ji.

  Two link members Li-1, Li are connected to each of the plurality of joint mechanisms Ji (i = 1,..., N).

  Each of the plurality of joint mechanisms Ji is configured to change the relative positions and postures of the two link members Li-1, Li connected to the joint mechanism Ji.

  In the present embodiment, all the joint mechanisms Ji are configured as rotary joint mechanisms. For this reason, in the following description, the relative position and posture of the two link members Li-1, Li connected to the predetermined joint mechanism Ji may be referred to as a joint angle ψ_i. Note that “the joint angle ψ_i changes” in the present embodiment corresponds to “the joint mechanism is displaced” in the present invention.

  In the present embodiment, all joint mechanisms Ji are configured as rotary joint mechanisms, but each joint mechanism Ji may be configured as either a rotary joint mechanism or a linear motion joint mechanism. Further, the number of joint mechanisms Ji may be an arbitrary number.

  The actuator 4 is provided in each of the plurality of joint mechanisms Ji, and outputs a driving force that displaces each joint mechanism Ji.

(1-2. Joint mechanism)
(1-2-1. Configuration of joint mechanism)
Next, details of the plurality of joint mechanisms Ji will be described with reference to FIGS. In the present embodiment, each joint mechanism Ji is a rotary joint mechanism having the same configuration.

  As shown in FIG. 2, the joint mechanism Ji includes a wire 11, a driving pulley 12a, a driven pulley 12b, and a transmission mechanism 8 that generates an elastic force and a viscous force between the pulleys 12a and 12b. .

  The reduction gear 7 connected to the actuator output shaft 4a of the actuator 4 is connected to the drive pulley 12a. The drive pulley 12a rotates in conjunction with the rotation of the actuator output shaft 4a by the rotational driving force (torque) applied from the actuator 4 via the speed reducer 7.

  Note that the speed reducer 7 may have an arbitrary structure, and for example, a speed reducer constituted by a harmonic drive (registered trademark) or a plurality of gears may be employed. Alternatively, the speed reducer 7 may include a mechanism that converts a linear motion into a rotational motion. In that case, as the actuator, for example, a linear motion actuator constituted by an electric motor and a ball screw, an electric linear motor, or the like may be employed.

  In the i-th joint mechanism Ji, the i-th link member Li rotatably supports the driving pulley 12a and the driven pulley 12b (not shown). In the i-th joint mechanism Ji, the i-1th link member Li-1 is fixed to the driven pulley 12b.

  The driven pulley 12b is juxtaposed on the side of the drive pulley 12a so that the rotation axis thereof is parallel to the rotation axis of the drive pulley 12a.

  The transmission mechanism 8 includes a characteristic variable mechanism 10 for changing the rigidity and viscosity between the pulleys 12a and 12b, and a wire 11 spanned between the driving pulley 12a and the driven pulley 12b.

  As shown in FIG. 3, the wire 11 has two extending portions 11a and 11b extending between the pulleys 12a and 12b, and portions other than the extending portions 11a and 11b are both pulleys 12a and 12b. Of the outer periphery of the outer periphery of the driving pulley 12a so that it does not slip to any place except the outer periphery of the driving pulley 12a (the portion facing the driven pulley 12b and the outer periphery of the driven pulley 12b facing the driving pulley 12a). It is wrapped around. Note that the wire 11 has some elasticity.

  The characteristic variable mechanism 10 is configured, for example, as shown in FIGS. That is, the variable characteristic mechanism 10 includes a rotating bar 14 having rollers 13a and 13b pivotally attached to both ends. The rotary bar 14 can rotate integrally with the rotary shaft 15 around the axis of the rotary shaft 15 fixed at the center thereof. The rotation shaft 15 is disposed in a position parallel to the rotation axis of the pulleys 12a and 12b at a position between the driving pulley 12a and the driven pulley 12b.

  The rollers 13a and 13b at both ends of the rotating bar 14 have their respective rotation axes oriented in parallel to the rotation axes of the drive pulley 12a and the driven pulley 12b.

  And the outer peripheral part of the inner end side (side facing the other roller 13b) of one roller 13a of the rollers 13a and 13b is one extending portion of the two extending portions 11a and 11b of the wire 11 The outer peripheral portion on the inner end side (the side facing one roller 13a) of the other roller 13b is in pressure contact with the other stretched portion 11b of the wire 11. In this case, each of the extending portions 11a and 11b of the wire 11 is curved at the press contact portion of the rollers 13a and 13b.

  The variable characteristic mechanism 10 further includes a gear (spur gear) 16 that is connected to the rotary bar 14 via a rotary shaft 15 so as to be rotatable integrally with the rotary bar 14, and a spring meshed with the gear 16. A worm 17, an electric motor 18 that rotationally drives the spring worm 17, and a cylinder 19 in which viscous oil is sealed are provided.

  The spring worm 17 is a spring member formed in a coil spring shape so as to be able to function as a worm gear, and is externally attached to the rotation drive shaft 18 a of the electric motor 18. One end of the spring worm 17 near the main body of the electric motor 18 is fixed to a spring seat member 20a fixed to the rotation drive shaft 18a. Accordingly, the spring worm 17 rotates integrally with the rotation drive shaft 18a of the electric motor 18, and the gear 16 rotates as the spring worm 17 rotates.

  The cylinder 19 has a cylindrical portion 21 disposed coaxially with the rotation drive shaft 18 a on the other end side of the spring worm 17. A rotation drive shaft 18a of the electric motor 18 passes through the inside of the cylinder portion 21, and the cylinder portion 21 is slidable in the axial direction along the rotation drive shaft 18a. The other end of the spring worm 17 is fixed to a spring seat member 20b fixed to the end face of the cylindrical portion 21 on the spring worm 17 side. Therefore, as the spring worm 17 expands and contracts, the cylinder portion 21 of the cylinder 19 slides in the axial direction of the rotation drive shaft 18 a of the electric motor 18.

  In addition, a piston 22 fixed to the rotary drive shaft 18 a is provided inside the cylinder portion 21, and an outer peripheral surface of the piston 22 is in sliding contact with an inner peripheral surface of the cylinder portion 21.

  Then, viscous oil is enclosed in two oil chambers 23 a and 23 b defined by the piston 22 inside the cylinder portion 21. These oil chambers 23 a and 23 b are communicated by a communication pipe 25 having an orifice portion 24. In this case, the orifice portion 24 can change the opening area by a valve mechanism or the like (not shown).

(1-2-2. Operation of joint mechanism)
The operation of the joint mechanism Ji having the above configuration will be described. When the spring worm 17 is rotationally driven by the electric motor 18, the rotating bar 14 is rotated via the gear 16 meshed with the spring worm 17. Therefore, the rotation angle (phase angle) of the rotating bar 14 can be controlled by the servo control of the electric motor 18. Here, in the following description, as shown in FIG. 3, the phase angle of the rotary bar 14 is the direction in which the rotary bar 14 extends (the interval between the rollers 13a and 13b), and the interval between the drive pulley 12a and the driven pulley 12b. Is defined as a rotation angle φ of the rotating bar 14 from a state perpendicular to the rotation bar 14.

  In a state where power transmission (transmission of rotational driving force) between the pulleys 12a and 12b is not performed, the phase angle φ of the rotary bar 14 is controlled to a predetermined angle value (for example, φ0 in FIG. 3). Assume a state in which the rotation of the rotation drive shaft 18a of the electric motor 18 (and hence the rotation of the spring worm 17) is stopped (hereinafter, this state is referred to as a reference state).

  In this reference state, when a rotational driving force (torque) is applied from the actuator 4 to the driving pulley 12a, a tension proportional to the rotational driving force is generated in one of the stretched portions 11a and 11b of the wire 11, and the tension The rotational driving force is transmitted from the driving pulley 12a to the driven pulley 12b.

  At the same time, due to the tension generated in one of the stretched portions 11a and 11b of the wire 11, both pulleys 12a and 13b are brought into contact with the roller 13a or 13b of the rollers 13a and 13b that are in contact with the stretched portion 11a or 11b. A translational force in a direction substantially orthogonal to the interval direction of 12b acts.

  For example, as shown in FIG. 3, when a torque τd in the counterclockwise direction is applied to the drive pulley 12a, a tension Te proportional to the torque τd (= τd / the effective rotation radius of the drive pulley 12a) ) Occurs, and the translation force F acts on the roller 13a by the tension Te. The magnitude of the translational force F is substantially proportional to the torque τd. Further, the tension Te in FIG. 3 indicates the tension acting on the roller 13a.

  When the phase angle of the rotating bar 14 in the reference state is not zero (for example, the situation shown in FIG. 3), the rotation is caused by the translational force acting on the roller 13a or 13b (hereinafter referred to as F). A rotational driving force (torque) acts on the bar 14. As a result, the drive pulley 12a rotates relative to the driven pulley 12b, and the rotating bar 14 rotates. As a result, the gear 16 meshing with the spring worm 17 rotates integrally with the rotating bar 14.

  In this case, the torque (hereinafter referred to as τa) acting on the rotating bar 14 due to the translational force F acting on the roller 13a or 13b is expressed by the following equation (122-1) with respect to the translational force F. Have the relationship. As shown in FIG. 3, φ0 is the value of the phase angle φ of the rotating bar 14 in the reference state, and Ra is the rotation radius of the shaft center portion of the rollers 13a and 13b around the shaft center of the rotating shaft 15. .

τa = F · sin (φ0) · Ra (122-1)
Since the spring worm 17 does not rotate in the situation where the torque τa is applied to the rotary bar 14 as described above, a part of the spring worm 17 (specifically, the meshed portion of the gear 16 and the electric motor 18 are rotated by the rotation of the gear 16. The portion between the side spring seat member 20a) is extended or shortened, and the spring worm 17 generates an elastic force corresponding to the amount of expansion / contraction.

  In this case, the amount of expansion and contraction of the spring worm 17 from the reference state, and hence the amount of rotation of the rotating bar 14 from the reference state (the amount of change in phase angle) is applied to the gear 16 by the elastic force (translation force) of the spring worm 17. The applied torque balances with the torque acting on the rotating bar 14 (= the torque acting on the gear 16) due to the translational force F acting on the roller 13 a or 13 b due to the tension of the wire 11. In this equilibrium state, the torque τd applied to the drive pulley 12a is transmitted to the driven pulley 12b via the transmission mechanism 8.

  The rotation amount of the rotating bar 14 from the reference state in the equilibrium state is Δφ [rad], the rotation radius of the gear 16 is Rb, the rigidity of the spring worm 17 (the elasticity generated per unit change amount of the expansion / contraction amount of the spring worm 17). If the force change amount is k_sp_w, the torque (hereinafter referred to as τb) acting on the gear 16 by the elastic force of the spring worm 17 in the equilibrium state is given by the following equation (122-2). It is done.

τb = k_sp_w · sin (Δφ) · Rb≈k_sp_w · Δφ · Rb (122-2)
From this equation (122-2) and the equation (122-1), the relationship between the translational force F in the equilibrium state and the rotation amount Δφ from the reference state of the rotating bar 14 is expressed by the following equation (122-3) Given by.

F = (k_sp_w · Rb / (sin (φ0) · Ra)) · Δφ (122-3)
Therefore, the translational force F acting on the roller 13a or 13b by the tension of the wire 11 is proportional to the rotation amount Δφ of the rotating bar 14 from the reference state.

  Here, the translational force F acting on the roller 13a or 13b by the tension of the wire 11 increases as the torque applied to the drive pulley 12a (and thus the torque transmitted to the driven pulley 12b) increases. Further, the relative rotation amount of the drive pulley 12a with respect to the driven pulley 12b (relative rotation amount from the reference state) increases as the rotation amount of the rotation bar 14 from the reference state in the equilibrium state increases.

  Therefore, in a steady state where the relative rotation amount between the pulleys 12a and 12b is kept constant, torque transmitted from the driving pulley 12a to the driven pulley 12b (torque applied to the driven pulley 12b) is expressed as τsp, When the relative rotation amount between the pulleys 12a and 12b is expressed as Δθ, a proportional relationship of the following equation (122-4) is approximately established between τsp and Δθ.

τsp = k · Δθ (122-4)
Therefore, the transmission mechanism 8 functions as a spring member that transmits power between the driving pulley 12a and the driven pulley 12b. The torque τsp corresponds to torque (hereinafter referred to as “elastic force torque”) τsp transmitted by the elastic force generated between the pulleys 12a and 12b by the transmission mechanism 8. In this case, k in the equation (122-4) is the ratio of the change in the elastic force torque τsp to the change in the relative rotation amount Δθ between the pulleys 12a and 12b.

  This k indicates the rigidity between the pulleys 12a and 12b. The larger the value of k, the higher the rigidity between the pulleys 12a and 12b (the difference in the amount of rotation between the pulleys 12a and 12b is less likely to occur. Means). The value of the rigidity k of the transmission mechanism 8 basically corresponds to the phase angle φ0 of the rotating bar 14 in the reference state, and the value of the rigidity k decreases as φ0 increases.

  In order to control the rigidity k_i of the transmission mechanism 8 to a desired rigidity (target rigidity) by a control device (not shown) configured by a CPU or the like, for example, the following is performed. First, a table in which the phase angle φ0 of the rotating bar 14 in the reference state is associated with the stiffness k is stored and held in a storage device such as a memory of the control device. Then, the control device acquires the phase angle φ0 of the rotating bar 14 in the reference state with respect to the target rigidity according to the stored table, and performs the electric operation so that the phase angle φ0 of the rotating bar 14 becomes the phase angle φ0. The motor 18 is controlled. Thereby, the rigidity k_i of the transmission mechanism 8 is controlled to be the target rigidity.

  Here, the electric motor 18, the spring worm 17, the gear 16, the rotating bar 14, and the wire 11 are collectively referred to as the elastic element 5. The rigidity k between the pulleys 12a and 12b is referred to as the rigidity k of the elastic element 5. Further, the relative rotation amount Δθ between the pulleys 12a and 12b becomes the elastic displacement amount of the elastic element 5 (that is, corresponds to the elastic deformation amount of the elastic element in the present invention).

  Further, in the transmission mechanism 8 of the present embodiment, when the rotary bar 14 rotates from the reference state, the cylinder portion 21 of the cylinder 19 slides relative to the piston 22 as the spring worm 17 expands and contracts.

  At this time, when viscous oil flows between the oil chambers 23a and 23b through the communication pipe 25 having the orifice portion 24, a viscous force serving as a resistance force against the sliding of the cylindrical portion 21 is generated. As a result, the rotation of the rotating bar 14 from the reference state, and consequently, a viscous force that is a resistance force to the relative rotation of the driving pulley 12a with respect to the driven pulley 12b is generated between the pulleys 12a and 12b. And this viscous force will change by changing the opening area of the orifice part 24. FIG.

  In this case, the viscous force generated in the cylinder 19 when the opening area of the orifice portion 24 is kept constant is proportional to the moving speed of the cylinder portion 21 with respect to the piston 22, and consequently the expansion / contraction speed of the spring worm 17. The expansion / contraction speed of the spring worm 17 is substantially proportional to the rotation speed of the rotary bar 14.

  Further, the temporal change rate of the relative rotation amount between the pulleys 12a and 12b, that is, the relative rotation speed between the pulleys 12a and 12b (difference between the rotation angular velocities of the pulleys 12a and 12b) Depending on the rotational speed, the greater the rotational speed of the rotating bar 14, the greater the relative rotational speed between the pulleys 12a, 12b.

  Accordingly, the relative rotational speed between the pulleys 12a and 12b is expressed as Δω_pulley [rad / s], and the torque (hereinafter referred to as viscous torque) applied to the driven pulley 12b by the viscous force between the pulleys 12a and 12b is τdp. When expressed as follows, a relationship of the following equation (122-5) is approximately established between Δω_pulley and τdp.

τdp = C · Δω_pulley (122-5)
Therefore, the transmission mechanism 8 also has a function of generating a viscous force between the driving pulley 12a and the driven pulley 12b. In this case, C in the equation (122-5) is a ratio of the change in the viscous torque τdp with respect to the change in the relative rotational speed Δω_pulley between the pulleys 12a and 12b, and is hereinafter referred to as a viscosity coefficient C.

  The viscosity coefficient C indicates the degree of viscosity between the pulleys 12a and 12b. The larger the value of C, the higher the viscosity between the pulleys 12a and 12b (viscosity generated between the pulleys 12a and 12b). Is likely to grow). The value of the viscosity coefficient C of the transmission mechanism 8 basically corresponds to the opening area of the orifice portion 24, and the value of C decreases as the opening area increases.

  In order to control the viscosity coefficient C_i of the transmission mechanism 8 to a desired viscosity coefficient (target viscosity coefficient) by a control device (not shown) configured by a CPU or the like, for example, the following is performed. First, a table in which the opening area of the orifice portion 24 is associated with the viscosity coefficient C is stored and held in a storage device such as a memory of the control device. Then, the control device acquires the opening area of the orifice portion 24 with respect to the target viscosity coefficient according to the stored table, and controls the opening area of the orifice portion 24 to be the acquired opening area. Thereby, the viscosity coefficient C_i of the transmission mechanism 8 is controlled to become the target viscosity coefficient.

  Hereinafter, the cylinder 19 and the orifice portion 24 are collectively referred to as the viscous element 6. The viscosity coefficient C between the pulleys 12a and 12b is referred to as the viscosity coefficient C of the viscous element 6.

(2. Characteristic variable range)
In the following description, in the case of explicitly representing a code regarding the i-th joint mechanism Ji (where i represents the order of the joint mechanisms when counted from the base body 2 toward the distal end portion 3), Add "_i" to

  In the present embodiment, a coordinate system fixed to the base 2 (hereinafter referred to as “base coordinate system”) is used unless otherwise specified. When explicitly expressing values related to the x-axis, y-axis, and z-axis in the base body coordinate system, “_x”, “_y”, and “_z” are added to the end of the code.

  A link member that collides with the object Obj is defined as a collision link member Lcoll. One or more joint mechanisms Ji between the base 2 and the collision link member Lcoll are defined as target joint mechanisms Ji.

  Note that the collision link member Lcoll in the present embodiment corresponds to a movable portion in the present invention. Further, any of the link members Li (i = 1, 2,..., N) having one or a plurality of joint mechanisms Ji between the base body 2 and the object Obj may collide, Any of these link members Li (i = 1, 2,..., N) can be a movable part in the present invention.

(2-1. Rigidity variable range)
According to various studies by the inventors of the present application, when the collision link member Lcoll collides with the object Obj, in order to prevent the entire joint mechanism Ji from being damaged, each target joint is satisfied so as to satisfy the following two conditions. It is necessary to be able to control the rigidity k_i of the elastic element 5 of the mechanism Ji.

(Condition 1)
In each target joint mechanism Ji, the kinetic energy (hereinafter referred to as “collision kinetic energy”) due to the displacement of the target joint mechanism Ji caused by the collision link member Lcoll colliding with the object Obj is used as the elasticity of the target joint mechanism Ji. The condition that all the elastic energy of element 5 can be converted.

(Condition 2)
The condition that the first time is equal to or longer than the second time in each target joint mechanism Ji.

  Here, the first time is “accumulated by the displacement of the target joint mechanism Ji” from “the time when the displacement of the target joint mechanism Ji caused by the collision link member Lcoll colliding with the object Obj”. The time until the displacement of the target joint mechanism Ji by the elastic energy of the elastic element 5 of the target joint mechanism Ji is started. In other words, the first time is a time during which the elastic element 5 of the target joint mechanism Ji absorbs the collision kinetic energy.

  The second time refers to the speed of joint displacement of the target joint mechanism Ji (hereinafter referred to as “joint” when the target joint mechanism Ji is displaced by the actuator 4 at the maximum acceleration A_max_i that the target joint mechanism Ji can achieve. This is the time required to change ω_i (referred to as “displacement speed”) by a speed obtained by reversing the direction of the relative joint displacement speed Δω_i of the target joint mechanism Ji caused by the collision link member Lcoll colliding with the object Obj.

  Here, the relative joint displacement speed Δω_i represents the amount of change in the joint displacement speed ω_i of each target joint mechanism Ji that is generated when the object Obj and the collision link member Lcoll collide with the object Obj. In the present embodiment, since the joint mechanism Ji is a rotary joint mechanism, the joint displacement speed ω_i is an angular speed.

  In each target joint mechanism Ji, when the above two conditions are satisfied, the following two effects are obtained. Thereby, damage to each target joint mechanism Ji due to the collision link member Lcoll colliding with the object Obj can be prevented.

(Effect 1: Effect of Condition 1)
The effect that in each target joint mechanism Ji, the impact on the target joint mechanism Ji caused by the collision link member Lcoll colliding with the object Obj can be absorbed by the elastic element 5 of the target joint mechanism Ji.

(Effect 2: Effect of Condition 2)
While the collision kinetic energy is absorbed by the elastic element 5 of the target joint mechanism Ji in each target joint mechanism Ji, the joint displacement speed ω_i of the target joint mechanism Ji is set to be relative to the target joint mechanism Ji due to the collision. The target joint mechanism Ji can be prevented from being forcibly displaced by the elastic energy of the elastic element 5 of the target joint mechanism Ji. The effect of being able to do it.

  For example, when detecting that the collision link member Lcoll collides with the object Obj, a control device (not shown) including a CPU or the like is configured to prevent the target joint mechanism Ji from being damaged by the collision. The rigidity k_i of the elastic element 5 of each target joint mechanism Ji is controlled so as to satisfy the conditions 1 and 2. Therefore, the change range of the stiffness k_i of the elastic element 5 of each target joint mechanism Ji (hereinafter, the minimum value of the range is referred to as the first stiffness k1_i and the maximum value is referred to as the second stiffness k2_i) It is set to satisfy the condition 2. Hereinafter, a method for setting the change range of the rigidity k_i of the elastic element 5 will be described.

(2-1-1. First rigidity)
In order to satisfy the condition 1, in each target joint mechanism Ji, the first stiffness k1_i of the elastic element 5 of the i-th target joint mechanism Ji is set such that the joint maximum elastic energy is equal to or greater than the joint minimum inertial collision kinetic energy. The

  Here, the joint maximum elastic energy is the i-th target joint when the elastic displacement Δθ_i of the elastic element 5 of the i-th target joint mechanism Ji is the maximum displacement Δθ_lim_i of the elastic element 5 of the i-th target joint mechanism Ji. This is the elastic energy of the elastic element 5 of the mechanism Ji.

  Further, the minimum joint inertial kinetic energy of the joint is the minimum value (hereinafter referred to as the following) that the inertia moment I_t_i of the i-th target joint mechanism Ji when the i-th target joint mechanism Ji is displaced can be taken. In the i-th target joint mechanism Ji, this minimum value becomes I_min_i (referred to as “i-th minimum moment of inertia”), and the maximum displacement speed ω_max_i that can be realized by the i-th target joint mechanism Ji when displaced by the actuator 4 Is the kinetic energy of the i-th target joint mechanism Ji when the i-th target joint mechanism Ji is assumed to be displaced.

  Here, in each target joint mechanism Ji, the moment of inertia I_t_i when the target joint mechanism Ji is displaced is, for example, from the position and posture of each link member Li obtained according to the joint angle ψ_i of each joint mechanism Ji. It calculates | requires according to Formula (211-1).

  However, the symbol “x” represents an outer product. I_k is an inertia tensor for rotating the k-th joint mechanism Jk when focusing only on the k-th joint mechanism Jk in the base coordinate system. Further, rgc_k (= (rgc_k_x, rgc_k_y, rgc_k_z)) is a position vector indicating the gravity center position of the k-th link member Lk, and r_i (= (r_i_x, r_i_y, r_i_z)) is the i-th target joint mechanism Ji It is a position vector indicating the position of the center of rotation. m_k is the mass of the k-th link member Lk. Further, a_i (= (a_i_x, a_i_y, a_i_z)) is a rotation axis vector representing the rotation direction of the i-th target joint mechanism Ji. a_i is appropriately set to indicate the rotation axis of the i-th target joint mechanism Ji.

  “|| I_k · a_i ||” in the expression (211-1) represents the link member Lk (k = i, i + 1,..., N between the i-th target joint mechanism Ji and the tip 3. −1, N), the moment of inertia when the link member Lk rotates around an axis parallel to the rotation center axis of the i-th target joint mechanism Ji and passing through the center of gravity of the link member Lk , Referred to as “first moment of inertia”). Therefore, I_A in the expression (211-1) represents each link member Lk (k = i, i + 1,..., N-1, N) between the i-th target joint mechanism Ji and the tip 3. Is the sum of the first moments of inertia at.

In addition, “|| a_i × (rgc_k−r_i) || ² · m_k” in Expression (211-1) is the link member Lk (k = i, k) between the i-th target joint mechanism Ji and the distal end portion 3. i + 1,..., N−1, N), the moment of inertia when the link member Li is rotated around the rotation axis of the i-th target joint mechanism Ji (hereinafter referred to as “second moment of inertia”). ). Therefore, I_B in the equation (211-1) is the link member Lk (k = i, i + 1,..., N-1, N) between the i-th target joint mechanism Ji and the tip 3. Is the sum of the second moments of inertia at.

  Note that, in each target joint mechanism Ji, the inertia moment I_t_i when the target joint mechanism Ji is displaced is not limited to that calculated according to the equation (211-1), but may be calculated using another arithmetic equation or the like. .

  Note that rgc_k changes according to the joint angle ψ of each of the first joint mechanism J1 to the k-1th joint mechanism Jk-1. Moreover, r_i and a_i change according to each joint angle (psi) of 1st joint mechanism J1-i-1th joint mechanism Ji-1. In addition, I_k and m_k are uniquely determined when the structure of the link mechanism 1 is determined. From the above, it can be seen that the moment of inertia I_t_i changes according to the joint angle ψ_i of each joint mechanism Ji.

  Therefore, the i-th minimum inertia moment I_min_i when the i-th target joint mechanism Ji is displaced is the i-th target joint mechanism in each of all the possible combinations of “joint angles ψ_i that each joint mechanism Ji can take”. Of the moments of inertia I_t_i when Ji is displaced, the smallest moment of inertia I_t_i is determined.

  The joint minimum inertial collision kinetic energy increases as the inertia moment I_t_i of the i-th target joint mechanism Ji when the i-th target joint mechanism Ji is displaced increases. The joint minimum inertial collision kinetic energy is the collision kinetic energy in a case where the inertia moment I_t_i of the i-th target joint mechanism Ji when the i-th target joint mechanism Ji is displaced is the i-th minimum inertia moment I_min_i. Therefore, under the condition that the stiffness k_i of the elastic element 5 of the i-th target joint mechanism Ji and the joint displacement speed ω_i of the i-th target joint mechanism Ji are constant, the joint minimum inertial collision kinetic energy is a value that the collision kinetic energy can take. It is the minimum value of.

  By setting the stiffness k_i of the elastic element 5 of the i-th target joint mechanism Ji to be equal to or higher than the first stiffness k1_i, the moment of inertia of the i-th target joint mechanism Ji is changed when the i-th target joint mechanism Ji is displaced. Any value that can be taken by the i-th target joint mechanism Ji and any amount that can change the joint displacement speed ω_i of the i-th target joint mechanism Ji can be taken when the i-th target joint mechanism Ji is changed. Even if the value of is the elasticity of the i-th target joint mechanism Ji so that the condition 1 is satisfied (so that the collision kinetic energy can be completely converted into the elastic energy of the elastic element 5 of the i-th target joint mechanism Ji) The rigidity k_i of the element 5 can be set.

  More specifically, in each target joint mechanism Ji, the first stiffness k1_i of the elastic element 5 of the i-th target joint mechanism Ji is set to be equal to or greater than the value obtained by the following equation (211-2).

  Here, Formula (211-2) indicates the stiffness k_i of the elastic element 5 of the i-th target joint mechanism Ji that satisfies the following Formula (211-3).

  In Expression (211-3), the left side represents the joint minimum inertial collision kinetic energy described above. The right side indicates the joint maximum elastic energy described above.

(2-1-2. Second rigidity)
In order to satisfy the condition 2, in each target joint mechanism Ji, the second stiffness k2_i of the elastic element 5 of the i-th target joint mechanism Ji is set so that the third time is equal to or longer than the fourth time.

  Here, the third time is the maximum value (hereinafter referred to as the i th target joint mechanism Ji) that the moment of inertia I_t_i of the i th target joint mechanism Ji can take when the i th target joint mechanism Ji is displaced. In the target joint mechanism Ji, this maximum value becomes “I_max_i” (referred to as “i-th maximum moment of inertia”), and from the time when the displacement of the i-th target joint mechanism Ji is started, accumulation is performed by the displacement of the i-th target joint mechanism Ji The time until the start of displacement of the i-th target joint mechanism Ji by the elastic energy of the elastic element 5 of the i-th target joint mechanism Ji.

  Note that the i-th maximum moment of inertia I_max_i when the i-th target joint mechanism Ji is displaced is the i-th target joint mechanism in each of all possible combinations of “joint angles ψ_i that each joint mechanism Ji can take”. Of the moments of inertia I_t_i when Ji is displaced, the largest moment of inertia I_t_i is determined.

  The fourth time is the joint displacement of the i-th target joint mechanism Ji when it is assumed that the i-th target joint mechanism Ji is displaced at the maximum acceleration A_max_i at which the i-th target joint mechanism Ji can be realized by the actuator 4. This is the time when the speed ω_i is changed by the maximum joint displacement speed ω_max_i of the i-th target joint mechanism Ji.

  Here, during the first time, the inertia of the i-th target joint mechanism Ji when the i-th target joint mechanism Ji is displaced under the condition that the rigidity k_i of the elastic element 5 of the i-th target joint mechanism Ji is constant. The larger the moment I_t_i, the larger the moment. The third time is a first time when the inertia moment I_t_i of the i-th target joint mechanism Ji is the i-th maximum inertia moment I_max_i when the i-th target joint mechanism Ji is displaced. Therefore, under the condition that the rigidity k_i of the elastic element 5 of the i-th target joint mechanism Ji is constant, the third time is the maximum length that can be taken by the first time.

  The second time increases as the amount of change in the joint displacement speed ω_i of the i-th target joint mechanism Ji increases under the condition that the rigidity k_i of the elastic element 5 of the i-th target joint mechanism Ji is constant. . The fourth time is a second time when the joint displacement speed ω_i of the i-th target joint mechanism Ji is changed by the maximum joint displacement speed ω_max_i of the i-th target joint mechanism Ji. Therefore, under the condition that the stiffness k_i of the elastic element 5 of the i-th target joint mechanism Ji is constant, the fourth time is the maximum length that can be taken by the second time.

  Thus, the second stiffness k2_i is set so that the third time, which is the maximum length of the first time, is equal to or greater than the fourth time, which is the maximum length of the second time. Therefore, even if the inertia moment I_t_i of the i-th target joint mechanism Ji is any value that the i-th target joint mechanism Ji can take, the amount by which the joint displacement speed ω_i of the i-th target joint mechanism Ji is changed is Any value that can be taken when the i-th target joint mechanism Ji is changed, so that the condition 2 is satisfied (so that the first time is equal to or longer than the second time), the rigidity of the i-th target joint mechanism Ji k_i can be set.

  More specifically, in each target joint mechanism Ji, the second stiffness k2_i of the elastic element 5 of the i-th target joint mechanism Ji is set to be equal to or greater than the value obtained by the following equation (212-1).

  However, (pi) shows a circumference ratio.

  Here, the equation (212-1) is the rigidity k_i of the elastic element 5 of the i-th target joint mechanism Ji that satisfies the following equation (212-2).

  In the expression (212-2), the left side is the third time described above. The right side is the fourth time described above.

  As described above, in each target joint mechanism Ji, when the i-th target joint mechanism Ji is displaced, the inertia moment I_t_i of the i-th target joint mechanism Ji is any value that the i-th target joint mechanism Ji can take. However, the condition 1 and the condition 2 are satisfied, even if the amount of change in the joint displacement speed ω_i of the i-th target joint mechanism Ji is any value that can be taken when the i-th target joint mechanism Ji is changed. In this way, the rigidity k_i of the elastic element 5 of the i-th target joint mechanism Ji can be set. Therefore, in order to prevent each joint mechanism Ji from being damaged by the collision link member Lcoll colliding with the object Obj, the rigidity k_i of the elastic element 5 of each target joint mechanism Ji can be set to an appropriate range.

(2-2. Viscosity coefficient variable range)
In each joint mechanism Ji, the viscosity coefficient C_i of the viscous element 6 is configured to be changeable within the range of the first viscosity coefficient C1_i and the second viscosity coefficient C2_i. Here, when it is assumed that the stiffness k_i of the elastic element 5 of the i-th joint mechanism Ji is equal to the first stiffness k1_i, the first viscosity coefficient C1_i indicates that the behavior characteristic of the i-th joint mechanism Ji is critical or overdamped. It is set to become the characteristic of. Further, the second viscosity coefficient C2_i is such that when the stiffness k_i of the elastic element 5 of the i-th joint mechanism Ji is equal to the second stiffness k2_i, the behavior characteristic of the i-th joint mechanism Ji is critical or overdamped. Set to be characteristic.

  Thereby, even if the rigidity k_i of the elastic element 5 of each joint mechanism Ji is changed to any rigidity k_i in the range of the first rigidity k1_i and the second rigidity k2_i, the changed rigidity k_i. On the other hand, the viscosity coefficient C_i in which the behavior characteristic of the i-th joint mechanism Ji is a critical damping characteristic or an excessive damping characteristic is included in the range of the first viscosity coefficient C1_i and the second viscosity coefficient C2_i.

  Therefore, for example, by controlling the control device, the viscosity coefficient C_i of the viscous element 6 of each joint mechanism Ji can be changed so that the behavior characteristic of each joint mechanism Ji becomes a critical damping characteristic or an overdamping characteristic. It is possible to prevent the behavioral characteristics of each joint mechanism Ji from becoming a damped vibration characteristic. Then, the occurrence of the vibration of the collision link member Lcoll corresponding to the damped vibration of each joint mechanism Ji is prevented, and the collision between the collision link member Lcoll and the object due to the elasticity of the elastic element 5 of each joint mechanism Ji is prevented. Is done. Thereby, damage to each joint mechanism Ji due to the collision link member Lcoll colliding with the object Obj can be prevented.

  Specifically, the first viscosity coefficient C1_i is determined according to the following expression (22-1), and the second viscosity coefficient C2_i is determined according to the following expression (22-2).

  However, in Expressions (22-1) and (22-2), ζ represents an attenuation ratio. The damping ratio ζ is set so that the behavior characteristic of the target joint mechanism Ji becomes a critical damping characteristic or an excessive damping characteristic (that is, ζ is set to 1 or more).

(3. Control)
Next, in the link mechanism 1 configured as described above, when the control device (not shown) detects that any of the link members Li may collide with the object Obj, each joint An example of a method for controlling the rigidity k_i of the elastic element 5 and the viscosity coefficient C_i of the viscous element 6 of the mechanism Ji will be described.

  Note that the control device detects that there is a possibility that any of the link members Li may collide with the object Obj based on information from an external sensor (such as a camera) (not shown). Then, when the possibility is higher than a certain value in any of the link members Li, the control device 30 may cause the link member Li that has a certain possibility or more to collide with the object Obj. It is estimated that.

(3-1. Rigidity)
In this case, in each target joint mechanism Ji, the control device has a rigidity k_i that satisfies the following expression (31-1) within a range in which the rigidity k_i of the elastic element 5 of the target joint mechanism Ji can be changed (condition 1). The target stiffness that is the target value of the stiffness k_i of the elastic element 5 of the target joint mechanism Ji so that the stiffness k_i that satisfies the following expression (31-2) or less (so that the condition 2 is satisfied) is satisfied. k_cmd_i is determined. In equation (31-1), the left side represents the above-described collision kinetic energy, and the right side represents the above-described joint maximum elastic energy. In the formula (31-2), the left side indicates the first time described above, and the right side indicates the second time described above.

  Here, the relative joint displacement speed Δω_i of the target joint mechanism Ji is the collision relative speed (relative between the collision link member Lcoll and the object Obj) output by the speed sensor (not shown) provided in the collision link member Lcoll. Is determined according to the following equation (31-3) according to ΔV (= (ΔV_x, ΔV_y, ΔV_z)).

Δω = Jcoll ⁺ · ΔV (31-3)
Here, Jcoll ⁺ is a pseudo inverse matrix of the Jacobian matrix Jcoll shown below. The Jacobian matrix Jcoll is a Jacobian matrix that defines the relationship between the displacement speed of the collision link member Lcoll and the joint displacement speed ω_i of the target joint mechanism Ji in the base coordinate system. When the relative joint displacement speed Δω_i of the joint mechanism Jcoll closest to the collision link member Lcoll among the target joint mechanisms Ji is represented as Δω_coll, Δω is represented by (Δω_1, Δω_2,..., Δω_coll). That is, Δω is a vector having all the relative joint displacement speeds Δω_i of the target joint mechanisms Ji as elements.

  Then, the control device controls the rigidity k_i of the elastic element 5 of each joint mechanism Ji so as to become the determined target rigidity k_cmd_i. Thereby, even if it is a case where the collision link member Lcoll collides with the object Obj, damage to each joint mechanism Ji can be prevented.

(3-2. Viscosity coefficient)
In each joint mechanism Ji, the control device sets the target viscosity coefficient C_cmd_i, which is the target value of the viscosity coefficient of the viscous element 6 of the joint mechanism Ji, to the following equation (32) according to the target stiffness k_cmd_i set as described above. )

  However, in Expression (32), ζ represents an attenuation ratio as in Expression (22-1) and Expression (22-2). The damping ratio ζ is set so that the behavior characteristic of the target joint mechanism Ji becomes a critical damping characteristic or an excessive damping characteristic (that is, ζ is set to 1 or more).

  Then, the control device controls the viscosity coefficient C_i of the viscosity element 6 of each joint mechanism Ji to be the determined target viscosity coefficient C_cmd_i.

  Thereby, the behavior characteristic of each joint mechanism Ji becomes a critical damping characteristic or an over-damping characteristic, and is prevented from becoming a damping vibration characteristic. Therefore, the vibration of the collision link member Lcoll according to the damped vibration of the joint mechanism Ji is prevented, and the collision between the collision link member Lcoll and the object Obj due to the elasticity of the elastic element 5 of each joint mechanism Ji is prevented. Is done. Thereby, damage to each joint mechanism Ji due to the collision link member Lcoll colliding with the object Obj can be prevented.

(4. Modifications)
In the present embodiment, the first stiffness k1_i is determined to be a value equal to or greater than the stiffness k_i obtained according to the equation (211-2) described above, but the value may be determined by another arithmetic equation or the like.

  Further, in the present embodiment, the second stiffness k2_i is determined to be a value equal to or less than the stiffness obtained according to the equation (212-1) described above, but the value may be determined by another arithmetic equation or the like. .

  Further, the joint mechanism Ji may be in an aspect not including the viscous element 6 as long as the joint mechanism Ji includes at least the elastic element 5.

  Further, when the joint mechanism Ji transmits power between the drive side link and the driven side link as long as the power is converted into an elastic force and a viscous force and transmitted, this embodiment It may be an aspect other than the aspect. For example, a conductive polymer actuator configured to be able to change the stiffness and viscosity coefficient may be used on a power transmission path between the drive side link and the driven side link.

  DESCRIPTION OF SYMBOLS 1 ... Link mechanism, Obj ... Object, 2 ... Base | substrate, 3 ... Tip part, Ji ... Joint mechanism, 4 ... Actuator, 5 ... Elastic element, 6 ... Viscous element, 11 ... Wire (elastic element), 14 ... Rotation bar ( Elastic element), 16 Gear (elastic element), 17 Spring worm (elastic element), 18 Electric motor (elastic element), 19 Cylinder (viscous element), 24 Orifice (viscous element), Δθ Elastic Displacement (elastic deformation), Δθ_i: Elastic displacement (elastic deformation), Δθ_lim_i: Maximum displacement (maximum deformation), k_i: Rigidity, C_i: Viscosity coefficient, k1_i: First stiffness, k2_i: Second stiffness , C1_i: first viscosity coefficient, C2_i: second viscosity coefficient, ω_i: joint displacement speed (displacement speed), I_t_i: moment of inertia, Lcoll: collision link member (movable part).

Claims (4)

One or a plurality of joint mechanisms provided between a base and a movable part movable with respect to the base; and an actuator for outputting a driving force for displacing the one or the plurality of joint mechanisms, Each of the one or more joint mechanisms is a link mechanism configured to transmit power via an elastically deformable elastic element configured to be variably controllable in rigidity.
The rigidity of the elastic element of each of the one or more joint mechanisms can be changed within a range of a first rigidity or more and a second rigidity or less set for each of the one or more joint mechanisms. Has been
In each of the one or more joint mechanisms, the first rigidity of the elastic element of the joint mechanism is that the elastic deformation amount of the elastic element of the joint mechanism is the maximum deformation amount of the elastic element of the joint mechanism. The elastic energy of the elastic element of the joint mechanism in a certain case is such that when the joint mechanism is displaced, the moment of inertia or the inertial mass of the joint mechanism becomes the minimum value that the joint mechanism can take and is displaced by the actuator. Is set to be equal to or greater than the kinetic energy of the joint mechanism when the joint mechanism is assumed to be displaced at the maximum displacement speed that can be achieved by the joint mechanism,
In each of the one or more joint mechanisms, the second stiffness of the elastic element of the joint mechanism can be determined by the moment of inertia or the inertial mass of the joint mechanism when the joint mechanism is displaced. Time from the time when the displacement of the joint mechanism is started to the time when the displacement of the joint mechanism is started by the elastic energy of the elastic element of the joint mechanism accumulated by the displacement of the joint mechanism. However, when it is assumed that the joint mechanism is displaced at the maximum acceleration that can be realized by the actuator, the displacement speed of the joint mechanism is more than the time when the maximum displacement speed of the joint mechanism is changed. A link mechanism characterized by being set to be. 2. The link mechanism according to claim 1, wherein when any one of the one or more joint mechanisms is defined as an i-th joint mechanism, the first of the elastic elements of the i-th joint mechanism. The link mechanism characterized in that the rigidity is set to be higher than the rigidity obtained according to the following equation (1).
However,
I_min_i: Minimum value of inertia moment or inertia mass of the i-th joint mechanism that can be taken by the i-th joint mechanism when the i-th joint mechanism is displaced ω_max_i: Realized when the i-th joint mechanism is displaced by the actuator Maximum possible displacement speed
x_lim_i: maximum deformation amount of the elastic element of the i-th joint mechanism The link mechanism according to claim 1 or 2, wherein any one of the one or more joint mechanisms is defined as an i-th joint mechanism, and the elastic element of the i-th joint mechanism is the link mechanism. The link mechanism characterized in that the second rigidity is set to be equal to or less than the rigidity obtained according to the following equation (2).
However,
I_max_i: Maximum moment of inertia or mass of the i-th joint mechanism that can be taken by the i-th joint mechanism when the i-th joint mechanism is displaced π: Circumferential ratio
A_max_i: Maximum acceleration that can be realized when the i-th joint mechanism is displaced by the actuator ω_max_i: Maximum displacement speed that can be realized when the i-th joint mechanism is displaced by the actuator In the link mechanism according to any one of claims 1 to 3,
Each of the one or more joint mechanisms is configured to transmit power via the elastic element and a viscous element configured to variably control the viscosity coefficient,
The viscosity coefficient of the viscous element of each of the one or more joint mechanisms is changed within a range of the first viscosity coefficient or more and the second viscosity coefficient or less set for each of the one or more joint mechanisms. Configured to be possible,
The first viscosity coefficient of the viscous element of each of the one or more joint mechanisms is a behavior characteristic of the joint mechanism assuming that the rigidity of the elastic element of the joint mechanism is equal to the first rigidity. Is set to be critically damped or overdamped,
The second viscosity coefficient of the viscous element of each of the one or more joint mechanisms is a behavior characteristic of the joint mechanism assuming that the rigidity of the elastic element of the joint mechanism is equal to the second rigidity. Is set to have a characteristic of critical damping or overdamping.