JP2004195576A - Flexible joint manipulator using functional fluid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a semiactive mechanism; to absorb a variation in sudden acceleration; to rotate while sliding in an external environment when a joint contacts with the external environment; to allow arrival at a target position; and to safely avoid from and contact with the external environment by applying a flexible mechanism composed of a neutral position returning means and a functional fluid to a joint of a manipulator by an actuator. <P>SOLUTION: A part of the joint has a flexible joint composed of a device 6 using the functional fluid having the semiactive function and a spring element 8. When the manipulator contacts with the external environment, a part of the joint can bend while relieving contact force and impact force between both by the flexible joint. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a robot manipulator, which is also used in the same area as a human, and relates to a flexible joint using a functional fluid, and more particularly, a part of the joint is provided with a neutral position return means. The present invention relates to a robot manipulator constituted by a device using a functional fluid having a semi-active function.
[0002]
[Prior art]
Research that requires cooperative activities with humans has been actively conducted, and establishment of a cooperative system between humans and robots has been studied. Since the robot exists in the same area as a human, the robot is placed in an environment where both interferences such as contact and collision must be assumed.
[0003]
Under such an environment, a conventional robot manipulator is required to use a highly rigid actuator (such as a motor using a gear having a high reduction ratio) due to a demand for precise control. The use of this highly rigid actuator has the following problems.
[0004]
For one thing, when moving delicate goods (such as water in a glass, dishes on a tray, etc.) The actuator must be moved slowly so that no speed occurs. For this reason, the operating speed has been restricted. Also, if the external environment (humans, structures, etc.) suddenly enters the planned orbit of the manipulator, the manipulator will collide violently with the external environment, so the mass inside the conveyed object will move violently, and delicate objects will move. Can not. For this reason, the manipulator is subject to restrictions as applied environmental conditions. In addition, if the external environment (humans, structures, etc.) suddenly enters the planned orbit of the manipulator, or if the manipulator stops due to a power outage, failure, or the like during joint work with the manipulator, the manipulator is a non-back driver. It is a mechanism that is difficult to push the external environment while colliding with the external environment, and it is not possible to safely reach the target position. For this reason, there has been a problem in reliability in ensuring safety and reliability of operation. Furthermore, when the external environment (humans, structures, etc.) suddenly enters the planned trajectory of the manipulator, the manipulator becomes a non-back drivable mechanism, and when the external environment (humans, structures, etc.) comes into contact. It is difficult to instantaneously reduce the collision force and the contact force. For this reason, improvement was required to ensure the safety of the human body.
[0005]
Further, as a conventional technology in consideration of safety, there is a technology in which a safety device such as a torque limiter (Japanese Patent Application Laid-Open No. 2001-003951) is incorporated in a joint. However, these also cause the following problems.
(1) When severe vibration occurs, a sufficient damping force cannot be obtained by the torque limiter, and the vibration cannot be suppressed. Therefore, it has been desired to improve the operation characteristics.
(2) When a torque limiter is used, each of the "transportation work state" (relatively high torque because reliable work is required) and "contact with the external environment" (appropriate relaxation of torque) is required. The torque cannot be properly controlled by judging the state. For this reason, a problem remains in performing torque control adapted to various operating states.
(3) When the vehicle collides with the external environment, the mass inside the conveyed object moves violently due to the excessive decrease in the damping force of the torque limiter, and the delicate conveyed object cannot move. For this reason, the application range is restricted.
(4) When a torque limiter is used, the torque cannot be controlled in accordance with the difference in vibration characteristics depending on the magnitude of the mass of the conveyed object and the properties of the external environment (mechanical impedance, pain threshold, destruction threshold). For this reason, a problem remains in performing torque control adapted to various operating states.
(5) The anisotropic damper used for the torque limiter requires a complicated configuration, and is likely to cause a failure. Therefore, there is a problem in simplifying the structure.
[0006]
[Problems to be solved by the invention]
The invention of this application is to solve the above problem, the problem of the vibration of the contact force with the external environment such as the human body, and the neutral position return means and the semi-active function when the manipulator comes into contact with the external environment. A part of the joint constituted by the device using the functional fluid having the function of reducing the contact force and the impact force with the external environment due to the effect of the functional fluid, and the inside of the conveyed object generated by the impact with the external environment An object of the present invention is to provide a robot manipulator capable of avoiding a steep movement of a heavy movement of a cell.
[0007]
It is still another object of the present invention to provide a system that performs torque control of a manipulator joint based on a threshold value of pain tolerance to a human body so as not to harm the human body and other external environmental objects.
[0008]
[Means for Solving the Problems]
The invention of this application has been achieved after finding that the following mechanism is required to solve the above problems.
(1) A kinetic energy dissipating mechanism is required in a part of the joint in order to suppress rapid fluctuation of the acceleration of the manipulator.
(2) When an external environment (human, etc.) suddenly enters the planned trajectory of the manipulator, it is necessary to provide a flexible mechanism on a part of the link so that the joint becomes back drivable. In addition, a return spring is required to reach the target position.
(3) A semi-active mechanism is required so that avoidance and contact with the external environment can be performed safely.
(4) Torque is determined by judging each state such as "transportation work state" (relatively high torque because reliable work is required) and "contact with external environment" (appropriate relaxation of torque). It needs to be properly controlled.
(5) When the manipulator comes into contact with the external environment, a mechanism and a system that can control the torque are required in order to promote the relaxation of the impact force and the contact force to the external environment.
(6) A semi-active mechanism is used to control the torque according to the difference in vibration characteristics depending on the mass of the conveyed object and the nature of the external environment (mechanical impedance, human pain threshold, target object destruction threshold). is necessary.
(7) The structure must be simple.
As described above, the invention of this application firstly includes a flexible joint composed of a device using a functional fluid having a semi-active function and a neutral position return unit in a part of a joint, and the manipulator is connected to an external environment. The present invention provides a robot manipulator (Claim 1) characterized in that, when the flexible manipulator comes into contact with the flexible joint, a part of the joint can be bent while relaxing the contact force and the impact force between the two. is there.
[0009]
The invention of this application is further embodied in an apparatus using a functional fluid having a semi-active function, in which the robot manipulator is configured as a two-link manipulator and forms a flexible joint provided in the second joint part. Using a clutch that uses ER fluid, and using a non-linear spring for the neutral position return means, and applying an electric or magnetic field to the functional fluid, the difference in vibration characteristics due to the magnitude of the mass of the conveyed object and the mechanical impedance of the external environment The joint torque can be semi-actively controlled according to the human pain threshold and the destruction threshold of the object (Claim 2), and the neutral position returning means is a coil spring or a tension spring (Claim 3). ) To provide a robot manipulator.
[0010]
Secondly, the invention of this application provides, as a control system for controlling the robot manipulator, a flexible joint having a flexible joint comprising a neutral position returning means and a device using a functional fluid having a semi-active function. A two-link robot manipulator, a link driving device that changes the torque of a part of a joint constituted by a functional fluid, and enables a two-link robot manipulator to be transported, and a stable viscosity coefficient set by a link. During the transport work, the allowable acceleration determination device that determines the allowable acceleration of the load, and when the load exceeds the allowable acceleration, or when the contact with the external environment of the manipulator is sensed, the status is appropriately determined and set. Condition repair controller that performs appropriate control to restore to viscous conditions, and manipulators that are avoided from the external environment When the spring restoring provides a control system 2 link robotic manipulator, characterized in that it comprises a suppressing arm vibration suppression control vibration of the arm (claim 4).
[0011]
Furthermore, the invention of this application embodies each device in the control system, and has a flexible joint composed only of a first joint and an ER clutch using a functional fluid having a semi-active function and a soft spring. A plurality of links that constitute a manipulator with a second joint; a highly rigid motor that drives the first joint via a driver; a high-voltage amplifier that controls the second joint; Each angle sensor for detecting the angle of two joints, a force sensor installed on the second link, a load cell for detecting the acceleration received by the ER clutch, and receiving and calculating each detection signal, via the driver and the high voltage amplifier unit The present invention also provides a control system for a robot manipulator comprising a control device for controlling a motor and an ER clutch.
[0012]
Hereinafter, the invention of this application will be described in more detail.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention of this application will be described.
The robot manipulator is configured as a two-link manipulator, but is not limited to two links, and can be implemented with more links.
[0014]
Devices that use a functional fluid with semi-active functionality that is incorporated into a portion of a joint can utilize an ER clutch. Here, as the functional fluid having the semi-active function, not only the ER fluid but also other functional fluids such as an MR fluid and a magnetic fluid can be applied.
[0015]
As for the neutral position returning means incorporated in a part of the joint, a non-linear spring may be used, and a coil spring or a tension spring may be used as the shape. When the extension of the second link is longer than the joint of the first link, a compression spring can be used because of the coupling structure between the tip of the extension of the second link and the joint of the first link.
The neutral position return means is a neutral position return means that acts to always return the bendable link to the neutral position, and may include an actuator with a small torque.
[0016]
Semi-active joint torque control by applying an electric or magnetic field to a functional fluid adapts to differences in vibration characteristics due to the magnitude of the mass of the carried object, mechanical impedance of the external environment, human pain threshold, and destruction threshold of the object Then, it can be controlled appropriately.
[0017]
Hereinafter, the invention of this application will be described in more detail with reference to the drawings.
[0018]
【Example】
The flexible joint manipulator using the functional fluid according to the invention of this application is configured as a simple two-link manipulator having a first joint and a second joint. The first joint is driven by a motor (actuator) having high rigidity, and the second joint is not provided with a driving unit, and is constituted only by a clutch using ER fluid and a soft spring.
[0019]
In the two-link manipulator of the invention of this application, as shown in FIGS. 1 and 6, the first link (4) is connected to the output shaft (3) of the motor (2) with a built-in gear mechanism installed on the support (1). Pivotally, the second link (5) is pivotally supported at one end of an output shaft (7) of an ER clutch (6) installed on the first link (4). In a two-link manipulator comprising a first link (4) and a second link (5) pivotally supported at one end of the first link (4), between the first link (4) and the second link (5). A spring (8) is interposed, and the second link (5) is mounted so as to be positioned and urged in a predetermined direction that is the longitudinal direction of the first link (4).
[0020]
An angle sensor (11) is installed at the tip of the output shaft (3) to detect the angle of the first joint. An angle sensor (11) is also installed at the tip of the output shaft (7), and the second joint is To detect the angle.
[0021]
A force sensor (12) is provided on the second link (5), and detects a contact force when the second link (5) comes into contact with a human body or an external environment body.
[0022]
A load cell (9) is provided at the other end of the output shaft (7) of the ER clutch (6), and a viscous torque generated between the ER clutch (6) and the first link (4) is detected.
[0023]
The control device (13) includes a personal computer (P / C), and detects the angle of the first joint and the angle of the second joint detected by the angle sensors (11) and (11), and the viscosity detected by the load cell (9). It receives and calculates a contact force detection signal detected by a torque and force sensor (12), applies a control voltage boosted via a high voltage amplifier (14) to an ER clutch (6), and applies a viscosity coefficient of the clutch. Control.
[0024]
The driver (10) is a drive mechanism for controlling the gear mechanism built-in motor (2).
[0025]
In the invention of this application, an ER fluid can be used as one of the functional fluids used for controlling the torque of the second joint of the flexible joint manipulator, and a non-linear spring is used as an example using the neutral position return means. Can be used.
[0026]
In the invention of this application, the ER fluid is a fluid whose viscosity is reversibly changed by application of an electric field, and is expected to be mainly applied to devices such as vibration system dampers and force senses, and does not generate external force by itself. Paying attention to having a function as a semi-active device, when applied to the operating mechanism of the manipulator of the present invention, a highly safe system can be constructed.
[0027]
In the invention of this application, a flexible joint mechanism is formed at a part of a joint of a robot manipulator by a device using a neutral position returning means and a functional fluid having a semi-active function. Can take three kinds of behaviors, Case 1, Case 2, and Case 3, as shown in FIG. 2, according to its role and state in use.
[0028]
“Case 1” in FIG. 2A schematically illustrates the behavior of the manipulator when interference from an external environment (a human, a delicate object, or the like) does not occur or does not occur. In this case, the number of joints effective for the work is reduced by the number of flexible joints. Therefore, this manipulator apparently functions as one link.
[0029]
Here, assuming a load attached to the link tip, a sudden increase in acceleration of the load can be suppressed by the energy dissipating action of the second joint. Therefore, it is effective for transporting a delicate object, such as a cup filled with water, that does not want the mass inside the transported object to move violently.
[0030]
Next, “Case 2” in FIG. 2B schematically shows the behavior when the manipulator is interfering with the external environment (human, delicate target, etc.) (M).
[0031]
This behavior is such that the moment the manipulator comes into contact with the external environment (M), the second joint is bent. This not only reduces the contact force between the manipulator and the external environment (M), but also keeps driving the first joint so that the second link (5) slides around the external environment (M). Acts to avoid.
[0032]
In this case, by controlling the torque of the ER fluid by the high voltage amplifier (14), the torque can be controlled in accordance with the properties of the external environment (M), for example, the mechanical impedance, the pain threshold, and the destruction threshold.
[0033]
Here, when transitioning from case 1 to case 2, a collision occurs between the external environment (M) and the manipulator at the initial stage. This collision force is caused by the action of a non-linear spring described later and the viscosity of the ER fluid. Is mitigated by being absorbed by the energy dissipating action of Even when moving a delicate cargo, it is also possible to control the viscosity of the ER fluid so that damage to the cargo is minimized in the event of a collision.
[0034]
Finally, “Case 3” in FIG. 2C schematically shows the behavior of the link 2 that attempts to restore the state of the case 1 by a spring after the link 2 has been avoided from the external environment (M).
[0035]
This behavior appears as a large vibration due to the effect of the spring (8) and the mass of the second joint. For this reason, it is necessary to consider the damping action due to the damping of the second joint, and the present invention makes it possible to control this vibration by the viscous damping effect of the ER fluid of the second joint. It is.
[0036]
Furthermore, when the transported goods fluctuate, for example, when carrying juice in a glass or a bowl on a tray, the container will move and spill because it exceeds a certain acceleration, but in such a case, To prevent spillage, the viscosity of the ER fluid is controlled so that it can respond to the movement of the center of gravity (related to the fluctuation of the moment of inertia) when the internal mass moves. Can be adapted. In addition, when the weight of the conveyed object changes (load change), the critical damping coefficient of the joint for the vibration control changes. This case can be easily coped with by changing the viscosity of the ER fluid. At this time, it is possible to attach an attenuator having a sufficiently constant viscosity by estimating the range in which the load fluctuates, but by making the viscosity variable, the time required for recovery can be shortened.
[0037]
Next, the mechanism of the flexible joint provided in the second joint will be described in more detail.
[0038]
As shown in FIG. 6, the second joint of the present application includes a rotary spring (8) and a clutch (6) using a uniform ER fluid.
[0039]
FIG. 3 shows the relationship between the rotation angle and the torque in the rotation system spring (8) used in the present invention. As shown in the drawing, the rotary spring (8) acts as a non-linear spring such that the torque is small at a small angle, and the torque increases as the angle increases. This non-linear spring action has the effect of reducing the contact force and the collision force generated in the initial stage of “Case 2”, and reliably returning the state from “Case 3” to “Case 1”.
[0040]
In the present invention, the homogeneous ER fluid is used as the working fluid of the clutch. The reason why the homogeneous ER fluid is used as the working fluid of the clutch is as follows. One is that it is easy to handle both the torque control by “Case 2” and the vibration control of Case 3, and the second is that the joints of the arm can be operated at a low speed even if the electric field continues to be applied due to a failure. If rotated, it can be avoided with a small contact force, and there is no settling of particles.
[0041]
FIG. 4 shows a schematic view of a clutch (6) using an ER fluid as an example.
[0042]
An input shaft (71) and an output shaft (7) that penetrate the housing (61) and protrude outward through the housing (61) are supported by ball bearings (63) and (64). A functional fluid (62) such as an ER fluid is sealed between the electrodes housed in the housing (61). The housing (61) is provided with slip ring portions (65) (66) for controlling the current of the electrodes.
[0043]
FIG. 5 shows the relationship between the rotational speed and the torque output of the clutch using the ER fluid shown in FIG. As is clear from this figure, the output torque of the ER clutch (6) according to the present invention is increased with an increase in the rotation speed, and the viscosity coefficient changes in accordance with a change in the magnetic field. Therefore, if this characteristic is used, the rotation speed and the magnetic field can be changed, whereby the change in the viscosity coefficient and the control of the torque can be performed.
[0044]
FIG. 6 shows a control system of these manipulators.
[0045]
A two-link flexible joint manipulator having a first joint driven by a motor having high rigidity (2) and a second joint having no drive and constituted only by an ER fluid clutch and a soft spring is provided by a control device ( 13) is controlled and driven via a motor (2) for driving the output shaft (3) of the first joint and a driver (10).
[0046]
The control device (13) includes an angle signal of the first joint and the second joint detected by the angle sensor (11), and a contact of the second link (5) detected by the force sensor (12) with a human body or the like. The calculation is performed in response to the force signal and the viscous torque signal generated in the ER clutch (6) detected by the load cell (9), and on the other hand, the ER clutch (6) is feedback-controlled through the high voltage amplifier (14), The viscosity coefficient of the clutch is controlled, and the motor (2) with a built-in gear mechanism is feedback-controlled via the driver (10).
<Case 1> Operation when interference from external environment does not occur As shown in FIG. 7, a target value is set, each link is driven, and a stable viscosity coefficient is set at that time. First, in the allowable acceleration determination step, if the movement of the conveyed object by the link is less than the allowable acceleration and there is no contact with the external environment, the viscous condition restoration control step is omitted and the process proceeds to the arm vibration control step.
<Case 2> Operation when manipulator is interfering with the external environment In the allowable acceleration determination step, if the movement of the load by the link exceeds the allowable acceleration, the viscous condition restoration control step is continuously executed. Then, an appropriate command voltage is applied by a computer to the ER clutch via an amplifier to control the viscosity. Thereafter, when the condition is satisfied in comparison with the set conditions, the process is led to the next arm vibration suppression control process, and the operation in the previous arm vibration control process is executed.
<Case 3> After avoiding the external environment, when the arm is not vibrated in the operation arm vibration suppression control step where the vibration is largely caused by the spring, the arm is driven until the target is reached. At this point, the driving of each link is stopped. On the other hand, when there is arm vibration, the link is driven until the target value is reached in a state where the viscous damping torque of the ER clutch is set and controlled. At this time, in the same manner as described above, the drive of each link is stopped at the time of arrival, and if it has not reached, it returns to the original position and repeats.
[0047]
From the above, the manipulator of the present application is controlled according to the following procedure for each case.
(1) The first joint is rotated by the motor while the second link is in contact with the external environment.
(2) The angle of the first joint is measured by an encoder provided on the motor.
[0048]
The rotation angle and the external force of the second joint are measured by a rotation angle sensor installed on the joint and a force sensor installed on the link, respectively.
[0049]
Further, the viscous torque of the ER clutch is measured by a load cell attached to the clutch output shaft.
(3) The measured values are taken into a personal computer (PC) and the next voltage is calculated.
(4) The viscosity coefficient of the clutch is controlled by applying the control voltage boosted by the high-voltage amplifier to the ER clutch.
[0050]
【The invention's effect】
As described above, according to the invention of this application, a sudden change in acceleration of a manipulator by an actuator can be absorbed by applying a flexible mechanism constituted by a return spring and a functional fluid to a joint. However, when the joint comes into contact with the external environment, the joint can rotate while sliding on the external environment to reach the target position.
[0051]
Further, by using the functional fluid, a semi-active mechanism is realized, and avoidance and contact with the external environment are safely performed.
[0052]
Furthermore, by making the joint a semi-active mechanism, differences in vibration characteristics due to the magnitude of the mass of the conveyed object caused by the flexible joint, the nature of the external environment at the time of collision, mechanical impedance, human sense threshold, destruction of the object The torque can be controlled according to the threshold value.
[0053]
By making the torque of the functional fluid variable, a reliable operation is required, so the "transportation operation state", which is a relatively high torque, and the "contact state to the external environment," where appropriate relaxation of the torque is required. And the like, and the torque corresponding to each state can be appropriately controlled.
[0054]
According to the invention of this application, the joint can be assembled with a simple structure because it is constituted only by the device using the functional fluid and the neutral position return means.
[Brief description of the drawings]
1 shows a schematic view of a robot manipulator of the present invention, (a) shows an overall schematic view of a two-link manipulator, and (b) shows a partially enlarged schematic view.
FIG. 2 shows the behavior of a robot manipulator having a flexible joint according to the present invention.
FIG. 3 shows a relationship between a rotation angle and a torque in the rotary spring of the present invention.
FIG. 4 shows a detailed view of the ER clutch of the present invention. FIG. 5 shows the relationship between the rotation angle of the ER clutch and the torque at each electric field value.
FIG. 6 shows an experimental system of the manipulator of the present invention.
FIG. 7 shows a flowchart when the manipulator is executed.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 support base 2 motor with built-in gear mechanism 3 output shaft 4 first link 5 2 link 5a extended end 6 ER clutch 7 output shaft 71 input shaft 8 neutral position return means 9 load cell 10 driver 11 angle sensor 12 force sensor 13 controller
P / C PC 61 Housing 62 Functional fluid 63 Ball bearing 64 Ball bearing 65 Slip ring section 66 Slip ring section

Claims (5)

A part of the joint is provided with a flexible joint composed of a device using a functional fluid having a semi-active function and a neutral position return means, and when the manipulator comes into contact with an external environment, the flexible joint makes contact between the two. A robot manipulator wherein a part of the joint can be bent while reducing a force and an impact force. 2. The device according to claim 1, wherein the robot manipulator is configured as a two-link manipulator, and a clutch using an ER fluid is used in a device using a functional fluid having a semi-active function and constituting a flexible joint provided in a second joint part thereof. By using a non-linear spring as the neutral position return means and applying an electric field or magnetic field to the functional fluid, differences in vibration characteristics due to the magnitude of the mass of the conveyed object, mechanical impedance of the external environment, human pain threshold, object A robot manipulator characterized in that the joint torque can be semi-actively controlled in accordance with the destruction threshold of the robot. 3. The robot manipulator according to claim 1, wherein the neutral position returning unit is a coil spring or a tension spring. A flexible joint two-link robot manipulator having a flexible joint comprising a neutral position return means and a device using a functional fluid having a semi-active function, and a torque of a part of the joint constituted by the functional fluid being variable and , A link drive device that can carry the work of the two-link robot manipulator, a permissible acceleration discriminator that determines the permissible acceleration of the conveyed object during the convey operation while setting the stable viscosity coefficient by the link, When acceleration is exceeded or when contact with the external environment of the manipulator is detected, a viscous condition restoration control device that appropriately determines the situation and performs appropriate control to restore the set viscous condition, and avoids from the external environment An arm vibration suppression control device for suppressing the vibration of the arm when the spring of the manipulator is restored. Control system of the robot manipulator. 5. The plurality of links according to claim 4, comprising a first joint and an ER clutch using a functional fluid having a semi-active function and a second joint having a flexible joint formed only by a soft spring. A high-rigidity motor for driving the first joint via a driver, a high-voltage amplifier for controlling the second joint, angle sensors for detecting the angles of the first joint and the second joint, A force sensor installed on the link, a load cell that detects the acceleration received by the ER clutch, and a control device that receives and calculates each detection signal and controls the motor and the ER clutch via a driver and a high-voltage amplifier unit are provided. A control system for a robot manipulator, characterized in that:

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