A vast DOF robotic car seat using SMA actuators with a matrix drive system

Long hours of driving cause the tissues to be pressurized for an extended period and result in considerable discomfort and driver fatigue. Periodically stimulating the tissues in contact with the car seat, as well as providing adequate ventilation and pressure relief may alleviate these problems. In this paper, we describe the design of a robotic car seat capable of actively redistributing the contact pressure on the tissue and thus providing relief to the weary driver. The distributed nature of the surface actuation and space limitations necessitate the use of a large number of actuators that must be confined to a small volume. We design and use Shape Memory Alloy actuator units, which can accomplish the above goals by virtue of their high power to weight ratio. Matrix architecture is used for the drive amplifier that can drive N² actuator units using only 2N switches and is thus suitable for vast degree of freedom systems in terms of scalability. The prototype car seat uses 16 SMA actuator units, which are driven in a matrix architecture using 8 switches. The actuators are compactly housed under the car seat and the force and displacements are transmitted to the flexible seat surface through a novel routing scheme. We create a distributed lifting motion of the seat surface in order to stimulate the tissue. A complementary distributed sinking motion of the seat surface is created in order to provide pressure relief and ventilation.