Improving actuation speed and controllability

With high-speed hydraulic proportional valves, the performance of existing cam phasing systems can be improved or the actuation mechanisms can be applied directly to engine valve actuation.

High-performance actuation mechanisms are key enablers for achieving higher efficiency and better performance in many systems. Common actuation mechanisms include electromagnets, piezoelectrics, motors with screws, and linear motors. In each mechanism, when linear on/off motion is considered, the actuator's entire mass must be accelerated each cycle. Researchers from Purdue University have developed a concept actuation system where the primary mass is always moving and the linear motion is caused by momentarily coupling the two masses to move together.

Piezoelectric actuators have a very fast response, a high-frequency bandwidth, reaching an upper limit of 25 kHz, and relatively high force capacity. However, their stroke lengths are small; they also require high driving voltages, and the material is still relatively expensive.