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Dealing with friction in a reusable 6 degrees of freedom adjustment mechanism with sliding contacts

Author: Klinkhamer, J.F.F.
Institution: Technisch Physische Dienst TNO - TH
Source:Hatheway, A.E., Optomechanics 2003, 7-8 August 2003, San Diego, CA, USA, 5176, 74-85
Proceedings of SPIE - The International Society for Optical Engineering
Identifier: 237416
Keywords: Electronics · Adjustment procedure · Degrees of freedom · Opto-mechanics · Calibration · Degrees of freedom (mechanics) · Kinematics · Lighting · Matrix algebra · Optics · Sensors · Wafer · Friction


Although the possibility of a 6 degrees of freedom adjustment based on a single body pulled onto on six adjustable supports follows directly from the kinematic theory, such mechanisms are seldom used in actual products. Two major drawbacks for the use of this solution are: Due to the sliding contact between the body and the supports, friction will occur and may inhibit movement. Coupling between the adjusted axes cannot be avoided, this may interfere with the necessity of an adjustment procedure with a limited number of iterations This paper presents a matrix calculation method that offers a prediction whether the body will move as required, depending on the position of the supports and on the magnitude of the friction. This method enables to check the functionality of a design. This method has been used in the design of several adjustment mechanisms consisting of a body pulled onto six supports. The matrix calculation method also allows predicting the movement of the adjusted body due to adjustment of the separate supports. Using this it is relatively simple to simulate the movements that an operator will observe, and in this way check whether an operator is capable to handle the couplings present in the adjustment. Using the simulation the adjustment procedure can be optimized.