Unless the gearbox is already designed, the actuator gearbox should be designed concurrent with the motor selection. This allows the overall system to be optimized. What being optimized means depends upon application. Optimal may mean lowest-cost, low size, or lowest weight. Right now, the focus is on defining the system level requirements. Criteria for optimizing the system by proper gear box design will be covered in the future.
Most systems operate at one more speed torque points. Typically a system has three main operating points:
1. A low load-high-speed operating point.
2. The primary operating point, which is system operates at the highest duty cycle, and
3. A high load operating point, which the system operates at low duty cycle.
These operating points are static speed operating points. All systems have some dynamic requirements, at a minimum, some acceleration is required; however dynamic requirements will be discussed at a later time.
Systems that decelerate [i.e. all systems] and systems that lower loads need to have controllers that are capable of handling the regenerated energy. Deceleration produces limited energy but load lowering can regenerate substantial energy. This energy must be dissipated or be returned to the power supply. Typically, if regenerator energy is not properly handed, the regenerated energy increases the controller internal supply voltage, commonly known as DC link voltage, until part failures occur.
Next: Performance curves