SetDrivingVelocities[linkage, {qi→vi, ..}] assigns new driving velocity (vi) values to qi driving variables and returns the updated LinkageData object .
The new driving velocities should be specified as list of rules, where on the left side of the rule are the driving variable or the derivative of the derivative with respect to the time and the right side specifies the values. Ex. {q1→1, q2→3} or {q'[t]→1, q2'[t]→2}SetDrivingVelocitiesTo has a HoldFirst attribute.