PID Control with Dual Actuators for Torque Distribution

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Solution Overview

Problem

Conventional PID controllers in industrial control systems often perform poorly due to their reactive nature and the need for larger actuators that handle both feedback and feedforward control, leading to packaging issues, increased maintenance, and reduced monitoring capabilities for wear.

Innovation Solution

Employing a secondary motor dedicated to open-loop feedforward control, allowing the primary motor to focus on smaller error corrections in feedback mode, thereby reducing peak torque requirements and enabling more efficient monitoring and maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If one actuator is used for both feedback and feedforward control, then device complexity is reduced, but the actuator size must be larger to handle peak torque requirements

Engineering Contradiction:

Improveactuator configurationVSAvoidpeak torque

Core Design Contradiction:

Device complexityVSForce

Solution Approach 1:

The control function is segmented into two separate actuators: a primary actuator for feedback control and a secondary actuator for feedforward control. This segmentation allows each actuator to be optimized for its specific function, with the secondary actuator handling the high peak torque requirements of feedforward control while the primary actuator handles smaller correction torques.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedforward control function is extracted from the primary actuator and assigned to a dedicated secondary actuator. This extraction allows the primary actuator to be smaller since it only needs to handle feedback corrections, while the secondary actuator handles the dynamic feedforward torque requirements.

Inventive Principle:

Principle #2Taking out (Extraction)

2Area of stationary object

If one actuator handles both feedback and feedforward control, then packaging space is reduced, but maintenance frequency increases

Engineering Contradiction:

Improvepackaging spaceVSAvoidmaintenance frequency

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

By segmenting the control functions into separate actuators, the system distributes the operational load and wear across multiple components. The secondary actuator handling feedforward control can be monitored independently, and wear can be identified more easily when functions are separated.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The secondary actuator serves as an intermediary that handles the high-stress feedforward control operations, protecting the primary actuator from excessive wear while maintaining compact packaging through coordinated control architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Difficulty of detecting and measuring

If one actuator performs both feedback and feedforward control, then monitoring for wear becomes more difficult, but system bandwidth is limited

Engineering Contradiction:

Improvewear monitoringVSAvoidsystem bandwidth

Core Design Contradiction:

Difficulty of detecting and measuringVSSpeed

Solution Approach 1:

Segmenting control functions into separate actuators enables independent monitoring of each actuator's performance and wear characteristics. The primary actuator's wear can be monitored through feedback control performance, while the secondary actuator's status can be monitored through feedforward control operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback control loop provides continuous monitoring of the primary actuator's performance and wear through position and velocity measurements. This feedback mechanism enables easy detection of wear in the primary actuator while maintaining high system bandwidth through coordinated control.

Inventive Principle:

Principle #23Feedback

4Stability of the object's composition

If PID loop gains are reduced to prevent overshoot and oscillation, then system stability is improved, but performance deteriorates

Engineering Contradiction:

Improvecontrol stabilityVSAvoidcontrol performance

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The feedforward control provides preliminary action by anticipating and applying the required torque before position errors occur. This allows the system to follow the desired trajectory proactively, eliminating the need for high PID gains that would cause overshoot and oscillation, while maintaining high performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The feedback control loop with reduced PID gains provides stable error correction without overshoot or oscillation. The combination of feedforward action and low-gain feedback achieves both high performance and stability by dividing the control functions appropriately.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10152033B2Proportional integral derivative control incorporating multiple actuators

Publication Date: 2018.12.11 VARIAN SEMICON EQUIP ASSC INC

AI summary

Embodiments of the disclosure provide proportional integral derivative control (PID) using multiple actuators. In one embodiment, a process includes providing a PID controller in communication with a primary actuator and a secondary actuator, the primary actuator and the secondary actuator coupled to a handler. The process further includes receiving position feedback and a specified trajectory for the handler, and generating a dynamic feedforward force command and a position correction command for the handler based on the position feedback and the specified trajectory. The process further includes providing, from the PID controller, the dynamic feedforward force command to the secondary actuator and the position correction command to the primary actuator.