Industrial Robot Axis Stopping with DC Braking Torque

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Solution Overview

Problem

Industrial robots face challenges in safely stopping axes to prevent coasting and sagging, especially during category 0 or 1 stops, due to the delay in mechanical brake engagement and high mechanical loads caused by existing braking methods.

Innovation Solution

The method combines electrical DC braking with short-circuit braking, using a separate DC source to generate a direct current that creates a static magnetic field and braking torque independent of motor speed, allowing for immediate and efficient stopping of the axes, even after drive energy is switched off.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical brakes are used to stop the axis, then the axis can be reliably stopped, but there is a release delay of 100 to 200 ms causing uncontrolled coasting

Engineering Contradiction:

Improvereliable stoppingVSAvoidrelease delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the mechanical brake system with an electrical braking system that uses a DC source to generate a static magnetic field in the motor, producing electromagnetic braking torque. This substitution eliminates the 100-200 ms release delay inherent in mechanical brakes, achieving immediate braking response when the drive energy is switched off.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a DC source as an intermediary component that provides direct current to the motor phases after drive energy is switched off. This DC source acts as a mediator between the control system and the motor, enabling continuous electromagnetic braking action during the period when normal drive power is unavailable, thus bridging the gap until the mechanical brake engages.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If drive power is switched off immediately, then the shutdown response is fast, but the axis coasts to a stop uncontrollably

Engineering Contradiction:

Improveshutdown response speedVSAvoidcontrolled stopping

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies preliminary braking action by generating a static magnetic field in the motor using DC current immediately when the drive energy is switched off. This preliminary electromagnetic braking prevents the axis from coasting uncontrollably, maintaining controlled stopping from the very beginning of the shutdown sequence rather than waiting for the mechanical brake to engage after a delay.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If mechanical brakes are used, then stopping is reliable, but high mechanical loads are placed on the braked components

Engineering Contradiction:

Improvestopping functionVSAvoidmechanical load on components

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces the mechanical braking system with an electrical braking system that generates electromagnetic torque through a static magnetic field. This substitution eliminates the high mechanical loads that would otherwise be imposed on the brake pads, brake disc, and associated mechanical components, while maintaining reliable stopping function through electromagnetic forces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Loss of time

If short-circuit braking is used, then coasting time is reduced, but braking torque depends on motor speed and sagging persists at low speeds

Engineering Contradiction:

Improvecoasting timeVSAvoidbraking effectiveness at low speed

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent changes the braking mechanism from speed-dependent short-circuit braking to speed-independent DC electromagnetic braking. By applying direct current to generate a static magnetic field, the braking torque becomes effective across all motor speeds including zero speed, eliminating the sagging problem that occurs with short-circuit braking at low speeds while maintaining reduced coasting time.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables quick and safe stopping of industrial robot axes, minimizing coasting and sagging, and reduces mechanical loads by using electrical braking to halt the motor before the mechanical brake engages, thus ensuring the mechanical brake functions as a holding brake during its triggering delay.

Implementation Method 1

using a separate DC source to generate a direct current that creates a static magnetic field and braking torque independent of motor speed

Methodology Applied

Scientific EffectElectromagnetic field generation: Electromagnet

Implementation Method 2

a direct current can be fed into at least one motor phase to generate a braking torque

Methodology Applied

Scientific EffectElectromagnetic torque generation: Lorentz Force

Data Source

PatentEP3017917B1Method and system for stopping axles of an industrial robot

Publication Date: 2021.11.03 KUKA DEUT GMBH

Figure 1~2
Figure 3~4

AI summary

The invention relates to a method and a system for safely stopping the axes of an industrial robot. The industrial robot comprises a control device (501, 502), power electronics (201, 202, 203) and a DC source (300) as well as at least one axis (700), which has an electric motor (100) and a mechanical brake (600) assigned. To stop the axis, a direct current is fed from the DC source into at least one motor phase of the motor, which generates a braking torque.