Dual-Stage Field Printer Robot Control for Sub-Millimeter Tracking
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Solution Overview
Problem
Traditional manual methods for printing construction layouts on construction sites are time-consuming and prone to errors, while existing mobile printing robots face challenges in maintaining sub-millimeter accuracy while moving at required speeds, leading to control issues and performance optimization problems.
Innovation Solution
A dual-stage controller with a decoupling filter is implemented for a mobile printing robot, which includes a differential drive and a linear actuator to control the position of a print head, allowing for separate control of steering and linear actuator movement, improving settling time and tracking accuracy by filtering the output of the slower steering stage using an approximation of the inverse of the faster actuator stage dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the robot moves at higher speeds to improve productivity, then printing speed increases, but tracking accuracy deteriorates
Solution Approach 1:
The control system is divided into two independent stages: an outer loop for trajectory planning and speed control, and an inner loop for real-time position correction. This segmentation allows the outer loop to operate at lower speeds for accuracy while the inner loop compensates for speed variations, enabling high-speed printing without sacrificing tracking accuracy.
Solution Approach 2:
The system implements a feedback mechanism where the inner control loop continuously monitors the actual print head position and compares it with the desired position from the outer loop. This feedback allows real-time correction of position deviations caused by high-speed movement, maintaining tracking accuracy even at increased printing speeds.
2Device complexity
If a single-stage controller is used to simplify the control system, then device complexity is reduced, but control precision deteriorates
Solution Approach 1:
The control system is divided into two independent stages: an outer loop for trajectory planning and speed control, and an inner loop for real-time position correction. This segmentation allows the outer loop to operate at lower speeds for accuracy while the inner loop compensates for speed variations, enabling high-speed printing without sacrificing tracking accuracy.
Solution Approach 2:
The controller uses dynamic switching between two control modes based on the operational phase. During acceleration and deceleration phases, the system engages both outer and inner loops for precise control. During constant velocity phases, the system can rely more on the inner loop, dynamically adjusting the control strategy to maintain precision while managing complexity.
3Adaptability or versatility
If the robot accelerates and decelerates frequently to improve responsiveness, then operational flexibility increases, but settling time increases
Solution Approach 1:
The outer control loop performs preliminary planning of acceleration and deceleration profiles before the actual printing operation. By pre-calculating optimal speed transitions and positioning maneuvers, the system minimizes unnecessary adjustments during printing, reducing settling time while maintaining operational flexibility for different printing scenarios.
Data Source
AI summary
A controller design for a dual input single output (DISO) system is applied to a robot for printing layouts at construction sites. The differential drive robot has a separately controlled linear actuator that moves the print head perpendicularly to the fore-aft axis of the robot. The output is the lateral position of the print head; the sum of the position of the linear actuator (faster stage) relative to a reference point on the front of the robot, which is determined by the steering of the robot (slower stage). Both are measurable. The controller coordinates the action of the separately controlled linear actuator and the differential steering to achieve fast convergence and sub-millimeter tracking. Simulations and experimental results demonstrate the effectiveness of the approach.