Parallel Kinematic Machine Tool Orientation via Shaft Joint
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Solution Overview
Problem
Current parallel kinematic machines (PKMs) face challenges in achieving high stiffness, large working range, and low weight, particularly in applications requiring high tool forces and tilting angles, as existing designs often compromise on stiffness and cost due to the need for bulky wrist actuators and complex structures.
Innovation Solution
A PKM design featuring a support platform with three support linkages and a tool base with a shaft joint, where tool linkages rotate the tool base shaft around axes relative to the support platform, distributing forces and torques efficiently to enhance stiffness and reduce weight, without the need for bulky actuators on the support platform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate wrist is mounted on the platform to obtain large tilting angles, then the tilting angle capability is improved, but the weight increases significantly
Solution Approach 1:
The manipulator is divided into separate functional modules: a parallel kinematic platform for positioning and a tool base with shaft joint for orientation. This segmentation allows each module to be optimized independently, eliminating the need for a heavy wrist assembly while maintaining large tilting angle capability through the shaft joint mechanism.
Solution Approach 2:
Instead of mounting actuators on the platform to achieve tilting (conventional approach), the invention inverts the approach by using a shaft joint at the tool base that is actuated by linkages connected to the platform. This reversal eliminates the need for heavy wrist-mounted actuators while achieving the same orientation capability.
2Adaptability or versatility
If a separate wrist is mounted on the platform to obtain large tilting angles, then the tilting angle capability is improved, but the stiffness is reduced
Solution Approach 1:
By separating the positioning function (parallel kinematic platform) from the orientation function (shaft joint at tool base), the invention eliminates the serial connection through a wrist that would reduce stiffness. The shaft joint is directly supported by the rigid parallel platform, maintaining high stiffness while achieving large tilting angles.
3Adaptability or versatility
If six linear actuators with one link between each actuator carriage and the platform are used, then six DOF parallel kinematics control is achieved, but the cost increases significantly
Solution Approach 1:
The parallel kinematic platform is designed to perform multiple functions: it provides both the positioning of the tool base and the actuation for the shaft joint orientation mechanism. This multi-functionality eliminates the need for separate actuators for each DOF, reducing the number of linear actuators from six to three while maintaining six DOF control capability.
4Weight of moving object
If tool linkages are used to rotate the tool base shaft, then the weight is reduced and stiffness is improved, but the device complexity increases
Solution Approach 1:
The tool linkages are integrated with the parallel kinematic platform structure, merging the orientation mechanism with the positioning system. The linkages use the platform's motion to achieve shaft rotation, combining multiple functions into a unified structure that reduces overall complexity despite the sophisticated kinematics.
Data Source
AI summary
A parallel kinematic machine, PKM, comprising: a support platform (17a), a first support linkage (SL1); a second support linkage (SL2) and a third support linkage (SL3), wherein the first support linkage (SL1), the second support linkage (SL2) and the third support linkage (SL3) together comprises at least five support links (8, 9, 10, 11, 12, 13). The PKM further comprises: a tool base (140) comprising a shaft joint (24, 40, 41, 200, 202, 262a, 262b), a tool base shaft (19) and a tool platform (17b). The tool base shaft (19) is connected to the support platform (17a) via the shaft joint (24, 40, 41, 200, 202, 262a, 262b), and wherein the tool platform (17b) and the tool base shaft (19) are rigidly connected. The PKM also comprises one or more tool linkages (TL1, TL2, TL3) each comprising a tool link (26, 31; 29, 32; 38) connected at one end via a tool base joint (25, 28, 37) to the tool base (140), and at the other end connected via a tool carriage joint (27, 30, 39) to a carriage arranged for movement along a path; and wherein each tool linkage (TL1, TL2, TL3) is configured to rotate the tool base shaft (19) around at least one axis relative the support platform (17), by transferring a movement of the respective tool linkage (TL1, TL2, TL3) to the tool base shaft (19).