21_Individual System FDD: Level 3 - Electrical/Control Subassembly
An initial FDD design of the Electrical/Control Subassembly for the Helping Hand is shown in Figure 1 below.
Figure 1: Level 3 FDD for Electrical/Control Subassembly
Some of the primary functions this system will be providing to the device are:
(1) It will approximate the user’s hand contraction based off of preprocessed EMG signals from the EMG processing system.
(2) It will supply pulling forces to the hand assembly based off of user-selected hand positioning as well as detected contracture signals.
(3) It will distribute power from the battery source into the EMG Processing, Motor Drivers, and Processor systems.
(4) It will convert 120V/60Hz home standard AC power into 9V DC power for charging the battery source.
(5) It will accept user inputs via switches which will turn the device on and off, activate/deactivate the device’s active assistance, activate/deactivate the device’s locking system, and select a predefined hand position.
(6) Finally, it will display the power state of the device (on/off; charging/full charge) as well as the device’s systems status (locking on/off; assistance on/off) with three indicator LED’s.
An initial layout of what the electrical/control system’s motor housing on the forearm might look like is shown in Figure 2 below. The springs pictured in the figure may be used to keep the motors from forcing a user’s hand open. However, there are other ways to interpret the amount of torque the motors are having to overcome so that if the torque resistance were too high, meaning the user’s hand contracture is not letting the hand open, then the motors could be shut off. The smaller boxes inside the housing layout are the motors.
Figure 2: Motor Housing Layout
