SEED Guides Sub-System Specification - Planar Mechanisms < >

Need the optimum time for each portion of the output, including dwells, be specified independently of the remainder?

Are the velocity and acceleration characteristics smooth and continuous? Are the magnitudes and locations of the extreme velocities and accelerations of all members acceptable?

Are absolute dwells needed? Would an approximate 'hesitation¹ be acceptable? (is any reversal of velocity acceptable?)

Need a specific displacement or velocity be obtained at a given input position?

Is good dynamic balance readily attainable?

Is the mechanical advantage adequate at all positions? Are there inherent dead-centre positions? Can the mechanism start from any position?

Does the geometry suit the relative positions of input and output? Is the available space adequate?

Design the mechanism for high strength/mass and stiffness/mass ratios. Parallel connection of members of planar mechanisms introduces twisting moments, cleavis (yoke) connections are preferable.

The natural frequency must not be a harmonic of the forcing frequency. The output acceleration must be a smooth continuous function (i.e. the jerk, d3y / dt3, must be finite throughout) to prevent shock loading and consequent vibration. Cam profiles must be finished to precision tolerances.

COMPARISON OF TYPES OF MECHANISM

SUITABLE APPLICATIONS OF MECHANISMS