DD219719B1 - DEVICE FOR WEIGHT COMPENSATION IN INDUSTRIAL ROBOTS - Google Patents

Description

For this 2 pages drawings

Field of application of the invention

The invention relates to a device for weight balance of moving elements in industrial robots using spring elements.

Characteristic of the known technical solutions

Technical solutions have already become known which at least partially offset the masses to be moved by industrial robots. The following principles are used:

1. the mass of the gripper arms are assigned counterweights; (e.g., PHM 4, IR 10, IR 60)

2. the mass of the gripper arms are compensated by counteracting tension or compression springs; (e.g., IR PHM 4 and PHM 40)

3. Use of so-called heart curves in the pivot points of gripper arms, act against the loaded with springs pressure rollers; (for example: DD-PS 0154282)

In the arrangement of countermeasures is first a complete balance of its own weight z. B. achieved a robot arm. This principle is technically useful when it comes to the counterweight to necessary functional elements, eg. B. electric motors, acts. However, if only "dead" masses come into consideration as countermeasures, there is the disadvantage that the total mass to be moved increases and as the mass moment of inertia increases, the dynamic properties of the system deteriorate.

In the arrangements with counteracting tension or compression springs, the dynamic disadvantages are avoided. However, these spring assemblies have the disadvantage that they have a fixed characteristic and differ significantly from the weight balance when moving in the case of articulated robots.

In the arrangement using heart curves, the required counter moments are achieved via the slope of the heart curve. As a result, the required characteristic curves can be reproduced exactly via the mathematically ascertained gradient curve. In the constructive and practical implementation of such devices, however, considerable design problems arise. In most cases, design-related pitch angle with less than 45 ° are required, whereby the applied by the pinch roller pressure force is a multiple of the restoring force to be generated. A disadvantage is the resulting high surface loads on the cam.

Object of the invention

The object of the invention is to avoid the disadvantages of the known arrangements.

Explanation of the essence of the invention

The invention has for its object to provide a device for weight balance in industrial robots, which realizes a compensation characteristic over a wide range of motion using springs while avoiding surface forces acting on cams.

According to the invention, compensation torques are generated over a wide range of motion by virtue of the fact that a specially shaped curve or cam plate upon rotation forms or unwinds a traction means tensioned by a spring. By changing the radius of curvature as a function of the angle of rotation of the cam and simultaneous change in the spring force, the required torque characteristic is realized.

By choosing the curve shape so desired characteristics can be realized.

With this solution, a mass balance is created, which avoids high surface forces on the cams used.

The weight compensation according to the invention can be accommodated in any joint of an industrial robot without substantially increasing the total mass.

embodiment

The invention will be explained in more detail with reference to an embodiment. Show it:

Fig. 1: a schematic diagram of the device according to the invention in conjunction with a screw jack using

rack and pinion; FIG. 2 shows a schematic diagram of the mass compensation device according to the invention for lifting movements in conjunction with a traction means; FIG.

3 shows a schematic diagram of the mass compensation device for a rotary joint; 4 shows end positions of the winding curves according to FIG. 1 and FIG.

a; b) end positions over a rotation angle φ of Fig. 1;

c; d) end positions over a rotation angle φ of Figure 3.

FIG. 1 shows the generation of a constant compensation torque for a lifting unit. The column 1, guided by guide rollers 2 carries a rack 4 and is in engagement with a gear 3. Axially on the gear 3, a cam 5 is fixed. The cam 5 with Kurvenbah 6 is connected to a traction means 10 and the traction means 10 is fixed by means of prestressed tension spring 7 on the frame 9. In Figure 2, the rack and the gear are replaced by a pull rope 13 and a guide roller 8. When moving the column 1, the pull cable 13 is wound on the curved path 6 of the cam 5, wherein at the same time biased with tension spring 7 traction means 10 on the guide roller is wound up or unwound. The traction means 10 may be a steel strip, steel rope and roller chain u.a. his.

The shape of the curve [r (cp) is to be chosen such that equilibrium of the device is and remains established by the biasing force F _{0 of} the tension spring 7 taking into account the spring characteristic in any position of the device generating moment of the wound-up Zugmittellänge (spring extension) and the effective radius of curvature r is proportional starting from the at sufficiently long traction means 10 and relatively long tension spring 7 approximately valid basic equation:

M (?) = Г (ψ) · F ₀ + г (ψ) ' C _F ' J -fr Op)

with M (φ) = moment generated at the curve

F ₀ = preload force of the tension spring

r (cp) = radius depending on the angle of rotation of the cam

C _F = spring constant

Under certain conditions, you can calculate the required curve step by step.

Analog can be a compensation device according to Fig.2füll realize a swivel joint (without translation for φ <180 °), wherein the waveform z. B. can be determined by iteration method. When sizing this compensation is important to ensure that concave curve pieces are avoided, since then the traction means 10 is no longer completely applied to the cam track 6 of the cam 5.

Claims (5)

Claim: 1. Device for weight balance in industrial robots using spring elements, characterized in that the element to be moved with a cam (5) is in communication, on whose curved path (6) under the spring force of a tension spring (7) standing traction means (10 ) is applied and the traction means (10) with the cam (5) is firmly connected. 2. Device for weight balance according to item 1, characterized in that for realizing a longitudinal or lifting movement in a rotary motion a rack '4) with a gear (3) is engaged and the cam (5) fixed to the gear ( 3) is connected, on whose cam track (6), the traction means (10) bears tangentially. 3. Device for weight balance according to item 1, characterized in that the cam disc (5) in the rotary joint (12) of a robot arm (11) is arranged. 4. Device for weight balance according to item 1 and 3, characterized in that the cam (5) is part of the robot arm and the cam track (6) on the lever arm (11) is formed.