JPH02106288A - Master manipulator - Google Patents

Abstract

PURPOSE:To enable the operating force of an operator to be very small, make an operating feeling favorable and improve an operating property by reducing or offsetting the inside friction torque of speed reduction mechanisms by means of alternating torque generated by servomotors. CONSTITUTION:The alternating torque of servomotors 5, 15 by means of energization is selected to be a value, e.g., to the extent of offsetting the inside friction torque of reduction mechanisms 4, 14. Hence, when the operating direction by an operator conforms to the direction of the alternating torque by the output shafts of reduction mechanisms 4, 14 of the servomotor 5, 15, it requires little operating force for the operator to operate a master manipulator.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention is a so-called pirate manipulator in which a force corresponding to an external force received on the slave side is transmitted to an operator on the master side as a force sensation, and is particularly compact and easy to operate. Concerned with excellent master manipulators. 2. Description of the Related Art Usually, a master-slave manipulator is composed of a master manipulator and a slave manipulator that are similar in shape to each other, and the master side is operated by an operator, and the slave side is driven in response. These master-slave manipulators have mainly been operated by remote control in environments that are dangerous and inaccessible to humans, such as nuclear power plants. In addition, by using a so-called pirate manipulator that transmits the external force received by the slave side to the master operator as a sense of force, it is possible to avoid injuries to both parties due to violent collisions with external obstacles, and to accurately perform delicate assembly tasks. I'm doing it. Generally, for this purpose, the master and slave are each configured as similarly as possible, with the constituent members having the same dimensional ratio, and each joint thereof is provided with a servo motor, an encoder, and a force sensor. Generally, in slave manipulators, particularly when handling heavy objects, a servo motor with a speed reduction mechanism is provided to drive each joint in order to increase the output torque and to reduce the size of the slave manipulator. Furthermore, in order to make the master manipulator smaller and lighter, a servo motor with a speed reduction mechanism is provided for driving each joint.

[Problem to be solved by the invention]

In the conventional technology, when a servo motor with a speed reduction mechanism is provided for driving the joint on the master side, the following problems occur. When the operator operates the master manipulator through the output shaft of the reduction mechanism of its servo motor, the efficiency seen from the output shaft of this reduction mechanism is low, so a large operating force is required to operate against the internal friction torque. Requires. For example, in a -g reduction mechanism, it is easy to transmit force from high speed to low speed, as seen in worms and worm gears, but conversely, the torque applied to the low speed shaft is not necessarily transmitted directly to the high speed shaft. do not have. This is because the transmitted force is canceled out by the frictional resistance of the meshing parts of the gears. In other words, a strong resistance effect occurs when force is transmitted in the opposite direction from low speed to high speed, and the higher the reduction ratio, the greater this effect is. As a result, the operator requires a large amount of force for operation, which cancels out the characteristic of the bilateral type in which force is transmitted to the master side in accordance with the external force received by the slave side, and the operator can feel the delicate force sensation from the slave side. You won't get it. Also, considering the variation in internal friction torque,
In particular, in the wrist-operated type where the force is weak, each joint cannot be moved smoothly, and the master manipulator cannot be operated according to the operator's intention. These problems are critical for remote control by master/slave manipulators. By the way, direct drive (which does not use a reduction mechanism)
A method using a direct-acting (direct-acting type) motor is also considered, but at present,
Its torque/weight ratio is smaller than that of a motor with a reduction mechanism (there is a disadvantage that it leads to an increase in the weight and size of the motor, which in turn leads to an increase in the weight and size of the master manipulator on which the motor is mounted). Increasing the size of this motor facilitates increasing the size of the master manipulator due to the gravitational balance required to improve operability on the master side. To provide a master manipulator which is compact and has excellent operability.

[Means to solve the problem] In order to solve this problem, the master manipulator according to the present invention It is equipped with a servo motor with a reduction mechanism that is energized so that predetermined torques in both forward and reverse directions are generated alternately at a predetermined period. A force corresponding to the external force received by the operator is transmitted to the operator. The value of the predetermined torque is, for example, a value that can cancel out the internal friction torque of the reduction mechanism of the servo motor. [For use]

The alternating torque of the servo motor due to the bias is selected to a value that can cancel out the internal friction torque of the reduction mechanism, for example. Therefore, when the direction of operation by the operator matches the direction of the alternating torque at the output shaft of the reduction mechanism of the servo motor at that time, the operator can operate the master manipulator with almost no operation force required. Additionally, if the direction of operation by the operator is opposite to the direction of the alternating torque at the output shaft of the servo motor's reduction mechanism, the operator cannot operate the master manipulator unless the operating force exceeds the alternating torque. . However, if the period of the alternating torque is selected to be a short period of 100 m5 or IS, when the operator's operating direction is opposite to the alternating torque direction, the operator will not operate for just the short period of time, and when viewed as a whole, it is actually This means that the master manipulator can be operated with extremely small operating force.

【Example】

Embodiments of the master manipulator according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of this embodiment, FIG. 1(a) is a side view of the main part of the embodiment with a partially inserted block diagram, and FIG. 1(b) is a plan view of the main part of the embodiment. , FIG. 2 is a basic configuration diagram of the master and slave manipulators commonly represented by motor function diagram symbols. First, in FIG. 2, 31 is the waist rotation axis, 32 is the shoulder vertical swing axis, 33 is the shoulder vertical swing axis, 34 is the wrist vertical swing axis, 35 is the wrist horizontal swing axis, and 36 is the wrist Each of the above rotation axes is common to both the master and slave sides. Reference numeral 37 indicates a gripping section for the operator on the master side, and reference numeral 38 indicates a hand section on the slave side. Further, 41 is an upper arm, and 42 is a lower arm, both of which are common to the master and slave sides. As shown in FIG. 2, in general, the master and slave manipulators have the same shaft configuration and the dimensional ratio of the arms are made constant so that they are similar in shape. This makes it possible to easily control position and force using an analog amplifier. On the other hand, so-called irregularly shaped master/slave manipulators in which the shaft configuration, arm size ratio, etc. are arbitrarily selected have also been extensively studied in recent years. One reason for this is that if the master side is made into, for example, a rectangular coordinate system, the intuitiveness of the operation will be excellent, and at this time, the slave side is made into a vertically articulated form according to the work object. in this case,
The movement of each joint is determined by solving mathematical equations, so
Digital control using a computer is required. Advances in microcomputers have made it possible to perform high-speed calculations with small manipulators, which brings us closer to practical application. In FIG. 2, for example, the operator faces the master manipulator, grasps and moves the grip part 37, and operates it to open and close the slave-side hand part 38. In an isomorphic slave manipulator, each joint operates similarly to that of the master manipulator. In FIG. 1, a master manipulator and a slave manipulator are connected via a differentiator and an amplifier,
Each side of the master and slave is represented by a set of joints and arms, so to speak, the master and slave sides are shown as one set of joints and arms.
Configure the slave manipulator. First, on the master side, 1 is an arm, 2 is a grip part, 3 is a joint part, 4 is a deceleration mechanism, 5 is a servo motor, 6 is an encoder, and 7 is a force sensor. On the slave side, 11 is an arm, 12 is a hand portion, I3 is a joint portion, 14 is a deceleration mechanism, 15 is a servo motor, 16 is an encoder, and 17 is a force sensor. Moreover, 21.22 is a difference device, and 23.24 is an amplifier. In FIG. 1, the operator holds the grip 2 and makes a swinging movement. This movement is controlled by a reduction mechanism 4° servo motor 5
The motor position (angle) is detected by an encoder 6 placed on the same axis. This position signal is matched with the position signal of the encoder 16, which is a slave-side motor position sensor, by a differentiator 21, and the difference is provided to a position control amplifier 23. As a result, the current of the slave-side servo motor I5 is controlled, the servo motor 15 is rotated, and the arm 11 is oscillated via the deceleration mechanism 14. As a result, the hand portion 12 is positioned at the same position as the master side. On the other hand, if the hand portion 15 or the arm 11 comes into contact with some kind of obstacle, the movement of the arm 11 is restricted. For this reason, force is applied to the slave-side joint 13 by the torque of the servo motor I5. This force is detected by a strain gauge type force sensor 17 attached to a cross-shaped beam as shown in the figure. This force signal is compared with the output signal of the strain gauge type force sensor 7 of the joint portion 3 of the same shape on the master side by a subtractor 22. By applying the deviation to the force control amplifier 24, the current of the master-side servo motor 5 is controlled, the servo motor 5 is driven, and the master-side arm 1 is moved ta via the deceleration mechanism 4. In the manner described above, the force acting on the slave side is transmitted to the operator. In this case, unless the position of the master side is changed, the force acting on the slave side can be transmitted to the master side at a constant rate. Note that when a force is applied, if the position on the master side changes, the position on the slave side will also change, and naturally the force acting on the slave side will also change. The operation of this embodiment will be explained with reference to FIGS. 1 and 3. 3 shows various torques for explaining the operation of the embodiment, FIG. 3(a) is a time chart of operating torque and friction torque, FIG. 3(b) is a time chart of alternating torque of the servo motor, (C) of the same figure is a time chart showing times when operations are possible and impossible. The meaning of each symbol is as follows. T: Operating torque, T
o: Motor shaft calculation value of T, Tf: Friction torque, Tm
: Alternating torque due to motor energization. In FIG. 1, it is assumed that the operator applies a constant operating torque T (indicated by a solid line) to the gripping portion 2 as shown in FIG. 3(a). In this case, since the speed reduction mechanism 4 is rotated from the output side, its efficiency is generally quite low. In other words, the torque that rotates the output shaft on the servo motor 5 side is:
Shaft conversion torque T. (displayed as a broken line). Here, if the friction torque of the five servo motors is Tf (indicated by a - dotted chain line), as shown in the figure, if Tr > To, the arm 1 will not move. Note that -Tf is the friction torque corresponding to the torque To when it is in the opposite direction. Now, let's energize the servo motor 5 (Fig. 3(t)).
As shown in FIG. At the same time, for ease of understanding, it is assumed that Tm=Tf. In Fig. 3(C), (To +7m) is shown as a double solid line, and when the torque Tm of the servo motor 5 acts in the same direction as the shaft conversion operating torque To applied by the operator, the torque Tm becomes the friction torque. By canceling out Tf,
The operating torque To by the operator remains unchanged. This operating torque To rotates the servo motor 5,
Arm l will move. Next, when the torque Tm of the servo motor 5 acts in the opposite direction to To, Tf and T
Since the combined resistance torque and torque m result in a large resistance torque, naturally the servo motor 5 does not move, and therefore the arm 1 also does not move. In this way, when a constant torque Tm is generated alternately in the forward and reverse directions on the servo motor 5, the servo motor 5 moves when the operation direction and the servo motor rotation direction match, and stops when the direction is opposite. Therefore, the entire system can be operated in the desired direction. That is, A indicates a time period in which operation is possible, and B indicates a time period in which operation is not possible. As is clear from the above description, in order for the operation to be performed, the relationship Tm > (Tf - To) needs to hold true. On the other hand, if Tm is too large, the fluctuations in force will become large and uncomfortable for the operator, so it is desirable that Tm be around TrnζTf. By the way, Zhou! tIIP
Considering human tracking ability, a distance of 100 m5 or more is sufficient, and depending on the inertia of the master side, even a distance of is or more may be effective. Further, when the period P is set to 100 m5 or less, the same effect as the method of removing or suppressing the influence of static friction by actively applying vibration, generally called dithering, can be obtained.

【Effect of the invention】

According to this invention, there are the following superior effects compared to the conventional technology. (1) The internal friction torque of the reduction mechanism is reduced or canceled by the alternating torque generated by the servo motor.
In practice, the operating force of the operator is extremely small, and the operating sensitivity is improved, resulting in excellent operability. (2) The existing servo motor for transmitting the external force received on the slave side is used, and no additional components are required.
Moreover, since the servo motor is equipped with a speed reduction mechanism, the entire morph including the speed reduction mechanism is smaller than that of a direct drive motor, and the master manipulator can be made smaller and lighter. (3) In relation to item (2), the cost performance of this master manipulator is extremely good since the incremental cost is small.

[Brief explanation of the drawing]

FIG. 1 schematically shows the configuration of an embodiment according to the present invention, FIG. 1(a) is a side view of the main part of the embodiment with a partially inserted block diagram, and FIG. The plan view of Figure 2 is the master commonly expressed with motor function diagram symbols. FIG. 3 is a basic configuration diagram of each slave manipulator, and shows various torsions for explaining the operation of the embodiment.
) is a time chart of operating torque and friction torque, and the same figure (
(b) is a time chart of the alternating torque of the servo motor, and (C) of the same figure is a time chart showing the time periods in which operation is possible and impossible. Description of symbols 1.11: arm, 2: gripping section, 3, 13: joint section, 4.14: deceleration mechanism, 5, 15: servo motor, 6.
16: Encoder, 7, 17: Force sensor, 12: Hand portion, 21.22: Differentiator, 23, 24: Amplifier. (b) Figure 1 Figure 2

Claims (1)

[Claims] 1) In a manipulator that transmits a force corresponding to an external force received on the slave side to an operator on the master side, a servo with a speed reduction mechanism is energized so that a predetermined torque in both forward and reverse directions is generated alternately at a predetermined period. A master manipulator comprising a motor, to which an operating force of the operator is applied via an output shaft of the speed reduction mechanism, and a force corresponding to the external force is transmitted to the operator.