RU2785422C1 - Adaptive compensation system for industrial robot - Google Patents

Abstract

FIELD: industrial robots.

SUBSTANCE: invention relates to an industrial robot with adaptive external load compensators, namely, to a compensator of a system with two degrees of freedom, including a rotational and a prismatic joint. The adaptive compensation system of an industrial robot contains at least one pair with two degrees of freedom, including a rotational and a prismatic hinge, on which a compensator is fixed, made in the form of springs, fixed on cables moving along at least two pulleys. The springs are made with a passive-adaptive movable attachment point.

EFFECT: invention provides compensation for gravity on prismatic connections at different orientations.

5 cl, 3 dwg

Description

FIELD OF TECHNOLOGY

The invention relates to an industrial robot with adaptive external load compensators, namely, to a compensator of a system with two degrees of freedom, including a rotational and a prismatic joint.

PRIOR ART

Industrial robots experience large static loads when working in large workspaces. These static forces are mainly generated by gravity, which means that a large proportion of the energy expended during operation goes to supporting the weight of the robot.

Various approaches have been proposed to compensate for gravity.

Compensation systems for industrial robots are widely known in the art.

A vertical movement device for balancing the mechanism is known (see SU1044591A1, publ. 09/30/1983) (1), containing a movable and fixed base, each having a groove parallel to the plane of the bases, a Nuremberg scissors hinge-lever mechanism, one ends of the free levers of which pivotally connected to the base with the possibility of rotation, and the others are installed in the grooves with the possibility of rotation and movement, and a balancing spring connected at one end to one of the levers of the mechanism. The device is equipped with a roller mounted on one of the bases and a flexible element enclosing the latter, connecting the lever with a balancing spring, the other end of which is fixed on the base.

The approach proposed in analogue (1) makes it possible to manipulate large payloads, however, it increases the total potential energy of the system.

Also known from the prior art is a spring mechanism chosen as the closest analogue, mainly for balancing vertical movement devices (see SU932005, publ. at one end a spring, a rotary block fixed on the same link, a flexible element enclosing the block and connected at one end to the free end of the spring, and a support element made in the form of a lever pivotally connected to the link on which the rotary block is fixed, and to the free end flexible element, the other link is made with a guide, with which the free end of the lever interacts.

Mechanism (2) achieves different results between full and partial weight compensation of the links. However, there remains a problem with prismatic joints, which is that gravity compensation is necessary for this type of joint, since the center of mass of the prismatic joint changes during movement.

SUMMARY OF THE INVENTION

Accordingly, there is a need to eliminate at least some of the disadvantages mentioned above. In particular, there is a need for an adaptive compensation system for an industrial robot that provides effective compensation for a system with two degrees of freedom, including a rotational and a prismatic joint.

This invention is aimed at solving a technical problem associated with increasing the efficiency of compensating for the forces of gravitation of systems, including including a rotational and a prismatic hinge.

The technical result of the invention is the creation of an adaptive compensation system for an industrial robot of increased efficiency.

The achievement of the claimed technical result is possible by means of an adaptive compensation system for an industrial robot, containing at least one pair with two degrees of freedom, including a rotational and prismatic hinge, on which a compensator is fixed, made in the form of springs, fixed on cables, moving along at least two pulleys .

The system is characterized by the fact that the springs are made with a passive-adaptive movable attachment point.

In a particular embodiment, the springs are connected to cables attached to a pin-splined mechanism, the cables interact with pulleys, one of which is fixed to a rack-and-pinion gear, while the gear is connected by a bevel gear to a self-locking worm gear, at the output of which a pulley is placed.

In a particular embodiment, the rotational joint compensator comprises a belt drive pulley with a slider, and a post on which springs are placed, one of which is connected to the slider located on the post, while the second spring is rigidly fixed to the housing.

In a particular embodiment, the compensator is equipped with a pin-spline mechanism connected to the spring cable, which provides the spring tension.

In a particular embodiment, the springs have a stiffness that balances the rotational and prismatic hinge.

The above and other objects, advantages and features of the present invention will become more apparent from the following non-limiting description of its exemplary embodiment, given as an example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The essence of the invention is illustrated by drawings, in which:

Fig. 1 – geometric representation of the system with two degrees of freedom;

Fig. 2 is a geometric representation of a system with two degrees of freedom with a prismatic hinge compensator;

Fig. 3 - geometric representation of the system with two degrees of freedom with, compensator prismatic and rotational hinge;

Positions in figures 1-3 indicate the following:

1- pulley;

2- pin-slotted mechanism;

3- rack-and-pinion gear;

4- bevel gear;

5- worm gear;

6- belt;

7- slider

These drawings do not cover and, moreover, do not limit the entire scope of options for implementing this technical solution, but are only illustrative material of a particular case of its implementation.

EMBODIMENT OF THE INVENTION

Declared the following system of adaptive compensation of an industrial robot using a gravity compensator for prismatic connections. The mechanism depends on the tension of the spring along with a combination of pulleys and gears. In addition, this mechanism is designed to compensate for the force of gravity on prismatic joints at various orientations. The proposed concept also includes gravity compensation for both hinges in the case of DOF mechanisms with a prismatic hinge mounted on a rotary hinge.

The system shown schematically in Fig. 1 consists of a pivot joint and a prismatic joint. The system consists of two masses m ₁ and m ₂ located at distances l _c1 and l _c2 from the center of rotation, respectively. The swivel hinge rotates at an angle q ₁ and the prism joint slides at a distance q ₂ , while the gravitational moment in the hinge of rotation is determined as follows:

τ ₁ = (l _c1 m ₁ +l _c2 m ₂ ) g cos(q ₁ ),

where τ ₁ is the torque of the rotating joint.

Since the prismatic hinge is sliding by the value q ₂ , we can transform the variable l _c2 as follows:

l _c2 = l _s0 + q ₂ ,

where l _s0 is the minimum distance between m ₂ and the center of rotation.

Regarding the force in the prismatic connection:

τ ₂ \u003d m ₂ g sin (q ₁ )

de τ2 - force force of the prismatic connection.

This equation shows that the force in the prismatic joint varies non-linearly with the angle of rotation of the first joint.

The pin slot mechanism shown in Fig. 2 is designed to compensate for such non-linearity. The mechanism consists of a spline-groove that rotates through an angle θ around the point O and moves linearly through the point O. The pin p is fixed at a constant vertical distance r from the point O and slides along the groove. As the point p is fixed, the distance between the slot and the point changes as follows:

s = r sin(θ),

where s is the distance between the slot and point O,

and r is the distance between the points O and p.

You can use this mechanism to compensate for the gravitational force in the prismatic hinge, as shown in Fig. 3. The pin mechanism is used to change the tension of the spring according to the angle of rotation q ₁ . In order to statically balance the force of the prismatic connection, the spring constant k and the pin spacing r can be chosen correctly.

k ₁ r sin(q ₁ ) = 1/2 m ₂ g sin(q ₁ )

And accordingly, we can choose the value of the spring stiffness k ₁

k ₁ \u003d m ₂ g / 2 r

Compensation for the pivot joint can be achieved with the construction shown in FIG. 3. It is possible to compensate for the gravitational moment in the pivot by placing a spring between points A and B. Point A is fixed at a vertical distance a from the ground, while point B has an initial offset b from the center of rotation and sliding on the link. Point B is attached to a slider mounted on a belt-pulley mechanism. The belt moves the slider a distance q* along the link, which means that the slip of point B is the ratio of the displacement of the prismatic hinge, which can be achieved by reduction. Another spring connects between points C and D, where point C is fixed at a vertical distance c and point D is fixed at a distance d along the link. What does the vector representing the position of points B and D do as follows:

This means that we can control the interval in which point B can slide as well as the location of this interval.

This system is a prism joint gravity compensation concept for robotic systems. The concept is based on the analytical separation of force expressions in the joints and their comparison with equivalent mechanical mechanisms using linear springs. By connecting these mechanisms to the joints of the robotic system, they can generate balancing forces that result in static equilibrium without the need for drive forces.

The industrial robot adaptive compensation system shown in Fig. 3 is designed for a pair with two degrees of freedom, consisting of a rotational and a prismatic joint. A compensator is fixed on the specified pair, made in the form of springs fixed on cables moving to pulleys. The compensator springs are made with a passive-adaptive movable attachment point.

The compensator springs are connected to the cables fixed on the pin-spline mechanism (2), the cables interact with the pulleys (1), one of which is fixed on the rack-and-pinion transmission (3), while the transmission gear is connected by a bevel gear (4) with a self-locking worm gear gear (5), at the output of which a pulley (1) is placed.

The rotary joint compensator shown in figure 3 contains a pulley (1) of a belt drive (6) with a slider (7), and a rack on which springs are placed, one of which is connected to the slider (7) placed on the rack, while the second the spring is rigidly fixed to the body.

The compensator is equipped with a pin-spline mechanism (2) connected to the spring cable, which can change the spring tension. The springs can be selected in such a way that their stiffness balances the rotational and prismatic hinge.

Designing a gravity compensator for prismatic joints is challenging due to the movement of the center of mass. Unlike links connected to swivel joints, which have a specific center of mass, prismatic joints change the location of the center of mass, which increases the non-linearity of the drive force when moving along an inclined axis. The movable spring attachment point helps to solve this problem by causing the balance mechanism to change in proportion to the range of motion. The use of worm gears is essential to this concept. The self-locking type worm gear can hold reverse torque by friction. This provides force isolation by introducing an internal reaction force that blocks any reverse torque. It acts as a one-way torque gate as it can transmit torque one way and blocks reverse torque. Another advantage of worm gears is that they have a high gear ratio, which reduces speed and increases torque, making movement resistance less significant.

INDUSTRIAL APPLICATION

The proposed devices are designed for a number of applications, including gravity compensation mechanisms with rotational and prismatic hinge.

Claims (5)

1. An adaptive compensation system for an industrial robot, containing at least one pair with two degrees of freedom, including a rotational and prismatic hinge, on which a compensator is fixed, made in the form of springs fixed on cables moving along at least two pulleys, characterized in that that the springs are made with a passive-adaptive movable attachment point. 2. The system according to claim 1, characterized in that the springs are connected to the cables attached to the pin-spline mechanism, the cables interact with the pulleys, one of which is fixed to the rack-and-pinion transmission, while the transmission gear is connected by a bevel gear with a self-locking worm gear , at the output of which a pulley is placed. 3. The system according to claim 2, characterized in that the rotary joint compensator contains a belt pulley with a slider and a rack on which springs are placed, one of which is connected to the slider located on the rack, while the second spring is rigidly fixed to the housing. 4. The system according to any one of claims 1 to 3, characterized in that the compensator is equipped with a pin-spline mechanism connected to the spring cable, providing spring tension. 5. The system according to any one of claims 1 to 4, characterized in that the springs have a stiffness that balances the rotational and prismatic hinge.

Images