Mixed Direct-Indirect Drive Control for Accurate Machine Positioning
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Solution Overview
Problem
The existing drive structures for machine elements, particularly those involving a transmission device, suffer from low rigidity, which results in reduced dynamics and positioning accuracy due to the limitations in the configuration of the controller structure.
Innovation Solution
A controller structure that determines a speed setpoint based on the position setpoint and actual position value, with a second speed controller adjusting the second drive's force setpoint, and additional pre-control values to enhance dynamics, including acceleration pre-control values converted into force pre-control values through filtering, to improve positioning accuracy and dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a transmission device is used to connect the second drive to the machine element, then the machine can handle high static and low-frequency loads, but the rigidity decreases leading to reduced dynamics and positioning accuracy
Solution Approach 1:
The control system is segmented into multiple independent controllers: a position controller for the second drive (indirect drive) and a speed controller for the first drive (direct drive). Each controller operates with its own control cycle and handles specific aspects of machine element positioning, allowing the system to simultaneously manage high loads through the transmission device while maintaining high positioning accuracy through direct drive intervention.
Solution Approach 2:
The controller structure implements dynamic control with different control cycles adapted to the characteristics of each drive. The position controller operates with a position control cycle suitable for the indirect drive, while the speed controller operates with a faster speed control cycle for the direct drive, enabling the system to respond dynamically to positioning requirements while handling mechanical loads.
2Device complexity
If the position controller determines speed setpoint and outputs it directly, then the control structure is simple, but the dynamics and disturbance correction capability are insufficient
Solution Approach 1:
The speed controller receives the speed setpoint from the position controller and performs preliminary processing by determining a resulting speed setpoint that incorporates feedforward components and disturbance compensation. This preliminary action prepares an optimized speed command before it is used to control the first drive, improving response dynamics without significantly increasing overall system complexity.
Solution Approach 2:
The speed controller acts as an intermediary between the position controller and the first drive. It receives the speed setpoint from the position controller, processes it through additional control logic including disturbance correction and feedforward terms, and outputs a refined resulting speed setpoint to the first drive, thereby enhancing system performance.
3Manufacturing precision
If additional speed controllers and determination devices are added to improve dynamics, then positioning accuracy and disturbance correction improve, but the device complexity increases
Solution Approach 1:
The speed controller is designed to perform multiple functions: it receives the speed setpoint from the position controller, determines the resulting speed setpoint with disturbance compensation, and outputs the refined speed command to the first drive. This multi-functionality consolidates several control tasks into a single controller, improving positioning accuracy without proportionally increasing device complexity.
Solution Approach 2:
The controller structure implements feedback mechanisms where the speed controller uses actual speed values from the first drive to adjust the resulting speed setpoint. This feedback loop enables disturbance correction and improves positioning accuracy by continuously adapting the control output based on actual system behavior.
Data Source
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AI summary
A first drive (2) acts directly on a machine element (1). A second drive (3) acts via a speed-changing device (4). A position controller (8) receives a position setpoint value (x*) and a position actual value (x) of the machine element (1) and determines a speed setpoint value (v*) for the machine element (1) from these variables (x*, x). A first determining device (11) receives the speed setpoint value (v*) and determines a resulting speed setpoint value using the speed setpoint value (v*). A first speed controller (9) determines a first force setpoint value (F1*) from the resulting speed setpoint value and the speed actual value (v) of the machine element (1) and controls the first drive (2) depending on said force setpoint value (F1*). A second speed controller (12) determines a second force setpoint value (F2*) from the resulting speed setpoint value and the speed actual value (v) of the second drive (3) and controls the second drive (3) depending on said force setpoint value (F2*).