Page 54 - Handbook of Biomechatronics

48 Reva E. Johnson and Jonathon W. Sensinger

Fig. 9 Illustrations of dielectric elastomer configurations: (A) two-degree-of-freedom
planar actuation, (B) one-degree-of-freedom planar actuation, and (C) bend actuation.
(Reproduced with permission from Mohd Ghazali, F.A., Mah, C.K., AbuZaiter, A., Chee, P.S.,
Mohamed Ali, M.S., 2017. Soft dielectric elastomer actuator micropump. Sensors Actuators
A Phys. 263, 276–284.)

Several terms should be defined when discussing transmissions.
A transmission scales forces and velocities, and this scaling ratio is typically
defined by a gear ratio stated as N:1. It is common to say that forces are
reflected from one side of the transmission to the other, implying that the
reflected force is scaled by the transmission ratio. Many transmissions have
static friction (commonly called stiction) that affects their efficiency and con-
trollability. Many transmissions also have backlash, in which over a brief
range of movement, movement of the input of the transmission does not
generate movement of the output of the transmission.
Many transmissions improve one attribute at the expense of others. For
example, compared with the range of forces and motion exerted by humans,
most motors produce too much speed but not enough force. Thus, the most
common reason to include a transmission is to convert the range of forces
and speeds the motor can produce to the range of forces and speeds used
by humans. However, many of these transmissions decrease efficiency