Articulated-Arm Robot Spindle Force Sensing for Machining Accuracy
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Solution Overview
Problem
Articulated arm robots experience inaccuracies during workpiece machining due to deformation caused by machining forces, which existing technologies fail to accurately detect and compensate for effectively.
Innovation Solution
The articulated arm robot design includes sensors at bearing points to detect radial and axial forces, with optional magnetic or hydrodynamic bearings for precise force measurement and compensation, allowing for real-time adjustment of the work spindle to counteract deformations and improve machining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are placed in the gearbox shaft to detect forces, then force detection is possible, but detection accuracy is reduced due to distance from the tool center point and increased moment of inertia
Solution Approach 1:
The patent introduces magnetic bearings as an intermediary mechanism between the work spindle and spindle housing. These magnetic bearings serve dual functions: supporting the work spindle and housing sensors that directly detect forces at the bearing points. This intermediary structure enables accurate force measurement without requiring direct sensor placement on the tool center point, thereby resolving the contradiction between detection accuracy and device complexity.
Solution Approach 2:
The patent replaces traditional mechanical contact bearings with magnetic bearings. This substitution allows for non-contact support of the work spindle while enabling direct force measurement through the magnetic field interactions. The magnetic bearing system provides both mechanical support and sensing capabilities, improving force detection accuracy while reducing the moment of inertia compared to traditional mechanical bearing arrangements.
2Speed
If magnetic bearings are used to support the work spindle, then high rotational speed and precise force measurement are achieved, but device complexity increases
Solution Approach 1:
The magnetic bearing system performs multiple functions simultaneously: it supports the work spindle mechanically, enables high rotational speeds through contactless operation, and provides force measurement capabilities through integrated sensors. By combining these functions into a single system, the patent achieves high speed and precise measurement while managing device complexity through functional integration rather than adding separate systems.
Solution Approach 2:
The patent utilizes changes in magnetic field parameters to control and measure the position and forces on the work spindle. By manipulating magnetic field strength and distribution, the system achieves high rotational speeds and precise force detection. This parameter-based control approach allows for dynamic adjustment and measurement without mechanical contact, resolving the contradiction between speed performance and system complexity.
3Device complexity
If conventional bearings are used to support the work spindle, then structural simplicity is maintained, but detection accuracy and rotational speed are limited
Solution Approach 1:
The patent replaces conventional mechanical contact bearings with magnetic bearings. This substitution eliminates mechanical friction and contact, enabling higher rotational speeds and more precise force measurement through non-contact sensing. The magnetic bearing system maintains structural elegance while dramatically improving measurement precision and speed capabilities compared to conventional bearing arrangements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise detection and compensation of forces and deformations, enhancing the accuracy and speed of machining processes while maintaining low mass inertia, allowing for high-speed machining and improved chip formation.
Implementation Method 1
the two bearing points are formed by magnetic bearings and the sensors are implemented by a measuring device for determining the field strength in the magnetic bearing
Implementation Method 2
the two bearing points are formed by a hydrodynamic plain bearing, and the sensors are implemented by a measuring device for determining the hydraulic pressure in the bearing points
Implementation Method 3
the sensors could be designed as piezoelectric elements
Data Source
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AI summary
The invention relates to an articulated-arm robot (1) and to a method for machining a workpiece by means of the articulated-arm robot (1). The articulated-arm robot (1) comprises: a base (2); a working head holder (7); a plurality of lever arms (3) which are arranged between the base (2) and the working head holder (7), the lever arms (3) being coupled to one another by means of revolute joints (4); a working head (8) which is arranged on the working head holder (7), the working head (8) comprising a working spindle (9) which is arranged in a spindle housing (13) and is mounted in the spindle housing (13) at least at a first bearing point (14) and a second bearing point (15). At least one sensor (16) for sensing a radial force (17) is formed at each of the first bearing point (14) and the second bearing point (15). At least one sensor (18) for sensing an axial force (19) is formed at at least one of the two bearing points (14, 15).