Robot Tool Head With Telescopic Shaft for Force Control
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Solution Overview
Problem
In robot-assisted machining processes, such as grinding and polishing, controlling the contact force between the tool and the workpiece is challenging due to the high inertia of the manipulator, leading to impulse-type contact forces and quality issues like overshooting and vibrations, especially when precision is required or delicate workpieces are involved.
Innovation Solution
A machine tool design that mechanically decouples the grinding machine from the manipulator using a linear actuator and a telescopic shaft with a gear mechanism, allowing for independent force control and reducing the impact of manipulator inertia, thereby maintaining a consistent contact force and minimizing vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the grinding machine is rigidly connected to the manipulator TCP, then the position control is simplified, but the high inertia of the manipulator causes impulse-type contact forces, overshooting, and vibrations
Solution Approach 1:
The system is divided into two independent control loops: position control (manipulator moving the grinding machine along trajectory) and force control (linear actuator controlling contact force). This segmentation allows each subsystem to be optimized independently, resolving the contradiction between simplified position control and precise force control.
Solution Approach 2:
A linear actuator is introduced as an intermediary element between the manipulator TCP and the grinding machine. This actuator mechanically decouples the high-inertia manipulator from the grinding machine, allowing independent control of position and contact force, thereby eliminating impulse forces and vibrations.
2Manufacturing precision
If a separate linear actuator is used to control process force, then force control is improved, but the device complexity increases
Solution Approach 1:
The linear actuator is integrated into the grinding machine structure rather than being a completely separate component. The actuator is mounted on the grinding machine's support structure and directly controls the tool engagement, merging force control functionality into the existing machine architecture to minimize additional complexity.
Solution Approach 2:
The linear actuator serves multiple functions: it controls the contact force between tool and workpiece, compensates for positioning errors, and provides mechanical decoupling between manipulator and grinding machine. This multi-functionality reduces the need for additional specialized components.
3Extent of automation
If the manipulator moves the grinding machine along a programmed trajectory, then automation is improved, but the high inertia causes vibrations and quality issues
Solution Approach 1:
The system transitions from a static rigid connection to a dynamic controlled connection through the linear actuator. The actuator actively adjusts the contact force in real-time during machining, allowing the system to adapt to varying workpiece geometries and maintain optimal cutting conditions throughout the automated process.
Solution Approach 2:
The force control system incorporates feedback from force sensors that monitor the contact force between the grinding tool and workpiece. This feedback is used by the linear actuator to continuously adjust and maintain the desired contact force, compensating for disturbances and ensuring consistent surface quality throughout the automated machining process.
Data Source
AI summary
The invention relates to a machine tool for robot-assisted surface finishing. According to one embodiment, the machine tool comprises a first support plate and a second support plate. The first support plate is designed for mounting on a manipulator. An output shaft for receiving a rotatable tool is mounted on the second support plate. The machine tool additionally comprises a linear actuator that acts between the first support plate and the second support plate, as well as a motor which is mounted on the first support plate. The machine tool additionally comprises a telescopic shaft with a first shaft portion and a second shaft portion that can be displaced relative to said first shaft portion. The first shaft portion is coupled to a motor shaft of the motor, and the second shaft portion as mounted on the second support plate. The telescopic shaft is coupled to the output shaft by means of a gear mechanism.