Servo Control System with Parallel Position Loops
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Solution Overview
Problem
Conventional servo control systems face a trade-off between critically damped transient response time and positioning accuracy, with PI controllers producing slower responses and P controllers prioritizing speed over accuracy, while also introducing noise and steady-state errors.
Innovation Solution
A servo control system with two parallel position close loops, using a position reference reduction circuit with a scale coefficient less than one, to generate separate input signals for P and I part controllers, enhancing transient response and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PI controller is used to achieve zero steady-state error, then positioning accuracy is improved, but transient response time increases and system response becomes slower
Solution Approach 1:
The patent divides the position control loop into two separate parallel loops: one for the proportional (P) part and one for the integral (I) part of the PI controller. Each loop has its own summing unit, controller, and feedback path. This segmentation allows independent optimization of transient response (through the P-loop) and steady-state accuracy (through the I-loop) without the performance degradation that occurs when using a conventional single-loop PI controller
Solution Approach 2:
The patent introduces a reference signal reduction circuit as an intermediary element that scales the position reference signal before it enters the P-loop. This intermediary component enables the P-controller to operate with an optimized reference level, improving transient response characteristics while the I-loop simultaneously ensures zero steady-state error through its own feedback mechanism
2Speed
If a P controller is used to achieve fast transient response, then response speed is improved, but steady-state error increases and positioning accuracy deteriorates
Solution Approach 1:
By segmenting the control system into separate P-loop and I-loop parallel paths, the patent allows the P-controller to operate independently for fast transient response while the I-controller independently eliminates steady-state error. This resolves the contradiction by distributing different control functions to separate parallel pathways rather than forcing a single controller to compromise between speed and accuracy
3Measurement precision
If conventional PI controller is used to improve positioning accuracy, then steady-state error is reduced, but system noise increases
Solution Approach 1:
The patent segments the feedback paths so that the I-loop operates with its own dedicated summing unit and feedback path, isolating the integral action from noise amplification issues. The P-loop with its reference reduction circuit also operates independently, allowing the system to achieve accuracy without the noise penalties associated with conventional PI controllers that process all signals through a single feedback path
Data Source
AI summary
A servo control system having a proportional (P) or a proportional plus integral (PI) position controller, which output signal represents an input speed reference signal for a speed close loop system with a speed controller detecting a speed deviation, derived from a speed feedback loop, which output signal represents an input current reference signal for a current close loop system with a current controller detecting a current deviation, derived from a current feedback loop, which controls an amount of the current flowing through a motor. The position controller detects the position deviation between a position reference signal and a position feedback signal separately for the P part controller, to produce a P part speed reference signal, and for the I part controller, to produce an I part speed reference signal, as a “two parallel-position outer loop feedback control system” and includes a position reference reduction circuit with scale coefficient less than one for the close loop with the P part controller. The P part controller and the I part controller connect to the summing unit, which sums the P part speed reference signal and I part speed reference signal, and its an output signal represents the speed reference signal for the speed close loop system.