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During my A-levels, I decided to do an Extended Project Qualification (EPQ). After considering the different EPQ options I decided to base my project around making an artefact. After a period of brainstorming different ideas, I ultimately decided to manufacture a robotic hand that could be remotely operated through hand gestures.
I started by researching the different fields in which robotics are prevalent, to gain an overarching understanding of the different features that are of interest in these different industries. Following this I also studied the anatomy of the human hand to explore how our hands are capable of achieving such a wide range of motion whilst remaining relatively compact.
Following the initial research phase, I started designing the robotic hand. Whilst the human hand is capable of a wide variety of motion the time and cost limitations led me to limit the hand motion to the flexure of the fingers and the hinging motion of the wrist.
To achieve the desired range of motion, I initially considered using individual motors for the actuation of each finger joint. This design was considered as it would give the hand more Degrees of Freedom (DoF), thereby resulting in a more flexible design that could be used in more applications. However, after evaluating the different motor options I could purchase, I concluded that the hand would need to be relatively large. To make my design more compact, I took inspiration from the human hand and instead considered using tendon-like elements to move the fingers. However, to simplify the construction, I considered attaching only the flexor tendons (on the bottom) to the servo and having an elastic string act as the extensor tendons (on the top).
To evaluate if this would work as intended I made a small model as shown beside. Through these tests, the design appeared to function as intended with only one limitation being evident. Primarily the finger was still susceptible to being flexed in the fully extended state as the elastic string used in the model was relatively compliant. To prevent this a stiffer elastic string would be required in the final build.
Before starting the full design process it was important to also consider the different electronics components and manufacturing methods that could be utilised.
Controller - After considering a variety of microcontrollers the Arduino Mega was chosen. This decision was made on the basis that the Arduino Mega has a wide variety of input and output ports which would facilitate the control of all the hand movements whilst also enabling remote operation through an additional module.
Actuators - In terms of the actuators Servos were primarily considered due to the ease of operation when combined with an Arduino microcontroller as they don't require additional controller boards like a stepper motor. After considering the different types of servos, the positional rotation servos were chosen over continuous rotation servos due to the higher positional accuracy.
Sensors - A variety of sensors were considered, to measure hand movements, ranging from potentiometers and flexural sensors to accelerometers and finally myoelectric sensors. After careful evaluation of the merits and issues associated with each sensor type, it was ultimately decided to proceed with the potentiometers.
Remote communications - To enable the remote operation of the hand, wifi and radio communications were considered. Whilst using WiFi communications could enable an exceptional operational range it would also increase the manufacturing time and complexity. Therefore in this build the NRF24L01 transceiver was considered for enabling the remote operation of the hand.
Manufacturing process - After evaluating the different facilities that were open for me to use I ultimately decided to use 3d printing to manufacture the robotic hand.
Proceeding to design the hand I decided to use Fusion 360. Whilst I initially attempted to design the whole hand from scratch, I later resorted to using the 3D models created by Gaël Langevin as part of the open-source project InMoov. However I designed my own sensor unit that incorporated potentiometers onto a glove allowing me to measure the finger movements.
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