4-DOF Parallel Mechanism Master-Slave System for Precision Needling
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Solution Overview
Problem
Current master-slave systems using series mechanisms suffer from low precision and dynamic inefficiency due to accumulated errors and increased inertia, making them unsuitable for precise tasks like needling in 3D spaces, and haptic devices face challenges in matching working spaces between master and slave devices with different DOFs.
Innovation Solution
A 4-degree of freedom (DOF) parallel mechanism is employed for both master and slave devices, featuring a spherical mechanism for 3-DOF rotation and a parallel link unit for 1-DOF translation, with reduced drivers and sensors, and a controller to synchronize movements and apply forces, enabling precise manipulation and force feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a series mechanism is used for master-slave system, then the working space is large and workability is good, but precision deteriorates due to accumulated errors from drivers connected in series
Solution Approach 1:
The parallel mechanism is segmented into multiple accessory chains (typically 4 chains) connecting the master base to the input unit. Each chain independently contributes to the overall motion, avoiding error accumulation while maintaining precision. The spherical mechanism is also segmented into multiple rotational joints that work together to achieve 3-DOF rotation.
Solution Approach 2:
The parallel mechanism structure inherently cushions against error accumulation by distributing the motion through multiple redundant chains. The closed-loop structure of the parallel mechanism prevents error propagation that occurs in series mechanisms, as each chain supports the others and compensates for individual chain deviations.
2Productivity
If a series mechanism is used for master-slave system, then the structure is simple, but dynamic efficiency deteriorates during high-speed work or while load is greatly changing
Solution Approach 1:
The parallel mechanism divides the driving function across multiple accessory chains, allowing each chain to handle a portion of the load and motion requirements. This segmentation enables high-speed operation and dynamic load handling without the inertia problems of series mechanisms, as the distributed structure reduces moving mass at each joint.
Solution Approach 2:
The parallel mechanism with spherical joint and accessory chains provides dynamic adaptability for high-speed work and varying loads. The closed-loop structure maintains structural rigidity during dynamic operations, enabling excellent performance during high-speed work or while load is greatly changing.
3Measurement precision
If haptic device uses series mechanism with sensor and motor at each joint, then the device can measure position and posture, but the motor movement increases inertia and obstacles user movement
Solution Approach 1:
The motors are extracted from the moving haptic device and fixed to the master base, separating the measurement function from the moving components. Only lightweight sensors remain on the accessory chains to measure joint angles, while the heavy motors stay stationary, eliminating the inertia problem that obstructs user movement.
Solution Approach 2:
Lightweight sensors act as intermediaries between the moving accessory chains and the stationary motors. These sensors measure the joint angles of the spherical mechanism and accessory chains, transmitting position and posture information to the controller without adding significant mass to the moving parts.
4Adaptability or versatility
If master device and slave device have different DOFs, then each device can be optimized for its function, but it is difficult to match working spaces of both devices
Solution Approach 1:
Both master and slave devices use the same 4-DOF parallel mechanism structure with spherical mechanism and accessory chains, making them universally compatible. This multi-functionality allows both devices to operate in the same 4-DOF working space (3-DOF rotation + 1-DOF translation), enabling precise master-slave coordination for tasks like needle insertion in 3D space.
Data Source
AI summary
A master-slave system using a 4-degree of freedom (DOF) parallel mechanism includes: a master device having a 4-DOF parallel mechanism which generates 1-DOF translation and 3-DOF rotation by the manipulation of a user; a slave device having a 4-DOF parallel mechanism which generates 1-DOF translation and 3-DOF rotation according to the movement of the master device; and a controller for receiving a behavior signal generated by the master device and outputting a driving signal to the slave device so that the slave device moves according to the movement of the master device. The master-slave system may be utilized as a remote needling robot with excellent manipulation and precision.