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4 PC Based Rapid Prototyping FES System
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4.3.2 Sensor Signal Processing
The normalized and offset compensated sensor signals are processed according to the
chosen control strategy. Of the five implemented control strategies push button control,
sliding potentiometer control, voice control, EMG event triggered control, and analog
EMG control only the EMG control strategies need a more sophisticated signal preprocessing. This will be discussed in Chapters 5 and 6. All other control strategies
require as pre-processing only linear gain and offset changes of the sensor signals.
Because of the modular concept of the software, further control strategies can easily be
added.
Figure 19: In the event triggered stimulation pattern generator software the trigger unit combined with
the rule based controller activates the stimulation patterns.
The event triggered stimulation pattern generator software shown in Figure 19 differs
from the continuously controlled stimulation software in the trigger unit (Figure 20) and
the stimulation pattern generation module (Figure 21). In the trigger unit up to 7
different trigger conditions can be defined. The recording channel, the processing
algorithm, and a trigger criterion can be chosen for each condition. In a sub-window one
of the trigger criteria: positive or negative slope, above or below threshold, peak or
valley, or double peak or double valley can be defined. In addition, the trigger
conditions (C1 to C7) can be operated with logical statements. Logical AND, OR and
NOT operations are used to build the logical statements. The first of the two statements
defines the grasp rule and the second statement defines the release rule.