Hybrid Drive Closed-Loop Control for Precise Machine Axes
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Solution Overview
Problem
The integration of direct and indirect drives in machine axes is complex due to size and cooling issues, and the high costs of direct drives limit system competitiveness, especially for multi-axis robots, where dynamics and positioning accuracy are compromised.
Innovation Solution
A closed-loop controller structure that includes inertia determination facilities to adjust pilot force values for both drives, allowing for cost-optimized dimensioning by dividing torque between geared and torque motors using scaling factors, and incorporating intalk compensation to improve positioning dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct drives are integrated into machine axes to improve dynamics and positioning accuracy, then positioning accuracy and axis dynamics are improved, but device complexity and cost increase due to size and cooling issues
Solution Approach 1:
The patent combines direct and indirect drive systems into a hybrid configuration where a first drive (indirect) and a second drive (direct) act on the same machine element. This merging allows the system to achieve the high positioning accuracy and dynamics of direct drives while using the cost-effective indirect drive for baseline operation, thereby improving performance without fully committing to the complexity and cost of complete direct drive integration.
Solution Approach 2:
The control system is segmented into multiple independent control loops: a position controller for the indirect drive, a speed controller for the direct drive, and coordination facilities that distribute torque between the two drives. This segmentation allows each drive to be optimized and controlled independently, managing the complexity of the hybrid system through modular control architecture.
2Speed
If direct drives are used to enhance axis dynamics, then axis dynamics are improved, but cost increases due to the high costs of direct drives
Solution Approach 1:
Instead of using direct drives for all operations, the system applies direct drive torque selectively through the third determination facility and scaling factors. The direct drive is activated partially to provide dynamic enhancement only when needed, while the indirect drive handles steady-state operations. This partial action reduces the overall cost and complexity while maintaining improved axis dynamics during critical operations.
Data Source
AI summary
A first drive acts on a machine element via a transmission and a second drive acts on the machine element directly. First and second closed-loop speed controllers determine respective first and second setpoint force values for the first and second drives with the aid of the difference between the setpoint speed value and of the actual speed value and activate the first drive and/or the second drive as a function of the respective first and second setpoint force values. Respective first and second pilot force values are determined from a first axis inertia scaled by a first scaling factor (α), and second axis inertia scaled by a second scaling factor (1−α).