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Case Study: Coordinate Measuring Robot

 

The PET worked in partnership with Nikon Metrology to provide important validation and design integrity assessments on the RCA project. The first task was to analyse the fundamental areas of the product that affect the key characteristics such as accuracy, motion control and environmental condition stability.

As the project continued, the research team were faced with a number of interesting design challenges. It was observed that the repeatability and accuracy of the measurement device was compromised when the arm passed through specific points in a certain way. These configurations, known as singularities, arise naturally due to the mathematics which underpins the physics of rotational joints and the coupling between the robotic exoskeleton and the passive inner measurement arm.

 

Robot Measuring Arm

 

Research at the University of Warwick showed that the inner arm was subjected to large constraining forces at the singularity positions, resulting in an undesirable deformation of the structure.

The research team sought solutions to circumvent this problem. By modelling the system as a coupled space of controls and configurations, the University of Warwick proposed a series of design principles for similar dynamic structures. Among the other studies that were carried out was the proof of concept for a proposed design review. This was a digital prototyping study in which a computer mock-up of the novel design was tested for its suitability for purpose. The so-called “RCA G3” was put through its paces in a virtual VDI test – the digital equivalent of an established standard metrology examination. After the university team demonstrated that the G3 model would pass this test Nikon commissioned the design.

 

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