Page 298 - Control Theory in Biomedical Engineering

A double pendulum model for human walking control 271

was fixed and the Impulse value was set by other values. After three strides,
stride time and stride length were measured to reveal the effect of Impulse on
these parameters. The same method was used for exhibiting the effect of k.
Figs. 2 and 3 exhibit the effect of these parameters on step length and step
time, respectively.
As shown in Figs. 2 and 3, step duration is much more affected by k and
step length by Impulse in the same way. So k and Impulse are considered as
control parameters for step length and step time, respectively.
A control method, so-called neural signals controllers (Huang et al., 2017),
was used for controlling step length and time. The step length controller for-
mulations are explained in Eqs. (6), (7).

0.55 0.55
0.5 0.5
Step time 0.45 Step time 0.45

0.4 0.4
0.35 0.35
0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 3 3.5 4 4.5 5 5.5 6 6.5 7
Impulse k
(A) (B)
Fig. 2 Effect of Impulse and k as control parameters on stride time are shown (A) As it
can be seen, changing of Impulse value has a negligible effect on stride time (B) Step
time is affected by k and it decreases when k increases.

0.8 0.8
0.75 0.75
0.7 0.7
Step length 0.65 Step length 0.65

0.6
0.6
0.55 0.55
0.5 0.5
0.45 0.45
0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 3 3.5 4 4.5 5 5.5 6 6.5 7
k
Impulse
(A) (B)
Fig. 3 Effect of control parameters (Impulse and k) on stride length are shown (A) Stride
length is increased by increasing Impulse value (B) Effect of k on stride length is much
less than Impulse.