Design of an adjustable cam based constant force mechanism

• A novel adjustable constant force mechanism (ACFM) based on cam mechanism is proposed.
• The mathematical model of the ACFM, which mainly consists of rigid bodies, is simple and accurate.
• The output force is close to the desired constant force and the scope of the output constant force is relatively wide.
• The proposed ACFM is easy to manufacture and does not tend to produce stress concentration.

A novel adjustable constant force mechanism (ACFM), which mainly consists of a linear spring and a cam mechanism (CM), has been proposed to passively regulate contact force. The CM is a linear negative stiffness mechanism and the constant force can be derived by paralleling the CM and the linear spring. To obtain the linear negative stiffness characteristic of the CM, the cam profile has been designed in detail. The magnitude of the constant force can be adjusted by preloading the linear spring. The mathematical model of the proposed ACFM, which doesn't contain complicated flexible members, is simple and accurate. To verify feasibility of the theoretical design procedure of the cam profile, a simulation of the ACFM has been carried out in virtual simulation software and the simulation results are consistent with the theoretical design procedure.

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