14 Feb 2018

"Success!! Finally managed to get an electrical current based force detection using the cheapest of parts. Wasn't quite sure if it would work out together so didn't say anything about but it's now working pretty good. The design is only just a proof of concept and there are many things with the design that still need changing so it may not be the perfect solution to fit the task.

Pros of the design: 
- Extremely cheap to produce with less than £8 worth of parts for the motor, driver and 3D printed parts. 
- The finger moves freely when forced closed or has bumped into something to prevent damage to the mechanism. 
- Current based feedback allows for the controller to calibrate the motor and to diagnose any issues the motor may have from long term use or damage. 
- Grip strength can be fixed or adjust through the controller between a soft to a semi firm grip. 
- Low cost for repair if the motor fails. 
- Entirely 3D printed except for the screws, motor and strings. 
- With a more intelligent current detection, the force sensing can be highly reliable.

Cons of design: 
- The motor is loud. Could be reduced with some rubber dampening. 
- Actuation speed is a bit slow but the motor can be driven at a slightly higher voltage or a different motor could be sourced. 
- Actuator length is a bit long but can be shortened by 3cm. 
- Power draw from the motor during actuation is a bit high at around 0.1-0.2A at 5V mainly due to the motor having to work against the elastic cord. A few design changes to the mechanism could help to reduce it. 
- The driver that is currently used barely fits the requirements of the motor and the application it is used. Another driver may be sourced or design changes to the mechanism and software could be done to work around it. 
- No speed control at the moment but may be able to be implemented using the current limit of the driver."

Jason Lee