Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001
Robots are machines, and as machines they are subject to all of the constraints of mechanics. Thus when dealing with many joints (prismatic or revolute) the physical limits of manipulator motion become evident. For the best solution, the limits of joint and actuator positions, velocity, acceleration, and jerk must be considered. The physical nature of the device also means that there are dimensions which must be considered, thus kinematics and collision avoidance come into play. When a robot makes any move, it expends energy to accelerate, hold and brake. This also means that the energy efficiency of the manipulator should be optimized, by reducing unnecessary expenditures of energy. Most importantly, if robots are to be cost effective, then their speed is of concern. In a high production situation, a cycle time that is 10% faster could save millions of dollars. Thus, time of path traversal can most often be the most important path planning factor.
- Velocity of Manipulator Links or joints.
- Joint Positions, Velocities, Accelerations and Jerks.
- Actuator Forces and Dynamics.
- Kinematics (this includes singularities).
- Time, when moving obstacles are involved.
Considering these factors, the problem may be formulated as a classical optimization problem, as many authors have done. These approaches usually produce good results, at the expense of computation time. Other methods are being found which trade off some of the completeness of the optimization to find solutions quickly.