Engineered Muscle Actuators: Cells and Tissues - Biomimetics: Biologically Inspired Technologies - page 260

Figure 9.3 (See color insert following page 302) Muscle Bioreactor Technology. Muscle identification, control,
and maintenance apparatus is shown with the primary sensors and actuators noted. The coarse positioning stage is
adjusted at the beginning of the experiment to accommodate different tissue lengths, but is typically kept at a
constant position during a particular contraction. The primary stage provides the motion that simulates the boundary
condition force law with which the muscle specimen pulls against. The vertical syringe has a suction electrode at its
tip that is connected to the stimulation electronics in the background. The encoder and load cell measure muscle
displacement and force, respectively, and are employed as sensory control inputs during FES control experimen-
tation. Silicone tubing recirculates solution via a peristaltic pump, while oxygen is injected in the loop.
primarily because the force generated by muscle is dependent on its mechanical state, namely its
length and velocity.
The second control loop for the bioreactor design of Figure 9.3 implements the electrical
stimulus (ES) control based on measurements of the muscle's mechanical response. This loop,
referred to as the ES control loop, offers simultaneous real-time modulation of pulse width,
amplitude, frequency, and the number of pulses per cycle. There is increasing experimental interest
in real-time control of muscles, primarily in the context of functional electrical stimulation (FES)
(Chizeck et al., 1988; Veltink et al., 1992; Eser et al., 2003; Jezernik et al., 2004). In these
investigations, attempts were made to control the response of muscle(s) and associated loads to a
desired trajectory by varying electrical stimulation parameters as a function of time. Electrical
stimulation patterns are typically square pulses characterized by frequency, amplitude, pulse width,
and number of pulses per trigger (considering the cases of doublets, triplets, or more generally
N -lets). For testing a variety of FES algorithms, the ES control loop is designed for real-time
modulation of these stimulation parameters as a function of a muscle's mechanical response,
including tissue length, contraction velocity, and borne muscular force.
9.11 CASE STUDY IN BIOMECHATRONICS:
A MUSCLE ACTUATED SWIMMING ROBOT
Biomechatronics is the integration of biological materials with artificial devices, in which the
biological component enhances the functional capability of the system, and the artificial component
provides specific environmental signals that promote the maintenance and functional adaptation of
the biological component. Recent investigations have begun to examine the feasibility of using
animal-derived muscle as an actuator for artificial devices in the millimeter to centimeter size scale