Redundant Parallel Mechanism for Singularity-Free Rotation
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Solution Overview
Problem
Spatial parallel mechanisms have limited rotational range of motion due to kinematic singularities, which restrict their orientational workspace, and scaling up the mechanism does not improve rotational range while increasing translational range.
Innovation Solution
A spatial parallel mechanism with kinematically redundant actuation, featuring three legs with distal and proximal joints that include passive revolute and spherical joints, and actuated joints, designed to avoid singularities by maintaining the distal rotational axes parallel and using a four-bar mechanism to support fingers with variable distance, allowing for increased rotational workspace.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the mechanism is scaled up to increase translational range of motion, then translational workspace is improved, but rotational range of motion remains limited by kinematic singularities
Solution Approach 1:
The patent changes the kinematic parameters by introducing redundant actuation degrees of freedom beyond the minimal required for platform positioning. This allows the mechanism to operate in redundant configuration spaces, enabling it to avoid singularities and achieve larger rotational workspaces without scaling up the physical dimensions of the mechanism.
Solution Approach 2:
The patent implements dynamic singularity avoidance by using the redundant actuators to actively adjust the mechanism's configuration in real-time. The additional degrees of freedom allow the system to dynamically reconfigure itself to escape singular configurations that would otherwise limit rotational motion, thereby expanding the operational workspace.
2Adaptability or versatility
If kinematically redundant actuation is added to increase rotational workspace, then rotational range of motion is improved, but device complexity increases
Solution Approach 1:
The patent makes the redundant actuators multi-functional by using them for both singularity avoidance and gripper actuation. The additional degrees of freedom serve dual purposes: maintaining the mechanism away from singular configurations and controlling the gripper's opening and closing motions, thereby reducing the need for separate dedicated actuators for each function.
Solution Approach 2:
The patent merges the singularity avoidance function with the gripper actuation function by integrating the gripper mechanism into the parallel structure. The redundant actuators that would otherwise be idle are combined with the gripper control, creating a unified system where the same mechanical elements perform multiple functions simultaneously.
3Ease of manufacture
If passive joints are used in the legs to reduce actuation complexity, then ease of manufacture is improved, but the ability to avoid singularities is reduced
Solution Approach 1:
The patent inverts the traditional approach by placing actuators at the distal ends of the legs rather than at the base. This unconventional actuation scheme, combined with passive proximal joints, allows the mechanism to achieve singularity avoidance through the coordinated motion of multiple legs with redundant actuation, while maintaining simple passive joints that are easier to manufacture.
Data Source
AI summary
A spatial parallel mechanism comprises a platform. Three or more legs configured for extending from a base or ground to the platform, each leg has a distal link, one or more distal joint providing one rotational degree of freedom (DOF) about a distal rotational axis, the distal joint connecting a distal end of the distal link to the platform. A proximal joint provides at least two rotational DOFs at the proximal end of the distal link. Assemblies of joints and links provide DOFs to each said leg between the proximal joint and the base or ground. The distal rotational axes of the three legs are parallel to one another.