Dextra

thingiverse

Dextra is a revolutionary robotic hand designed for printability, offering an affordable and open-source alternative to commercial prosthetic hands. Beyond its intended use as a prosthesis, Dextra can also be utilized in education, research, or various applications within the field of robotics due to its adaptable grip, compact size, mechanical simplicity, and ease of replication. The core design element of Dextra revolves around the finger module, consisting of a compact linear actuator based on a geared DC micro motor, position feedback provided by a magnetic encoder, and the printable finger itself. This modular design is replicated across the four fingers of the hand, with the thumb featuring a variation of the same architecture. To minimize size and mechanical complexity, Dextra's fingers are underactuated, meaning they possess more degrees of freedom than actuators. Each finger module boasts three degrees of freedom controlled by one motor, while the thumb enjoys two degrees of freedom driven by a single motor. Furthermore, the abduction/adduction motion of the thumb is independently managed through a servomotor. The movement of Dextra's fingers is governed by a position control loop. A PID loop guides each finger, taking a predetermined position as input and utilizing feedback from magnetic quadrature encoders to adjust the actual position driven by DC motors. To experience Dextra in action, viewers can access videos showcasing its functionality at the following links: https://www.youtube.com/watch?v=N3UU5vtAwHg, https://www.youtube.com/watch?v=Uz6x0zFXkCchttps://www.youtube.com/watch?v=L_VyQa0jCiI. Detailed information regarding Dextra's design and operation can be found on its hackaday.io project page (https://hackaday.io/project/9890-dextra) and Github repository (https://github.com/Alvipe/Dextra.git). Bill of Materials: Printable Parts: - 5x Spool.stl - 4x Motor_holder.stl - 4x Proximal.stl - 4x Middle.stl - 4x Distal.stl - 1x Motor_holder_thumb.stl - 1x Proximal_thumb.stl - 1x Distal_thumb.stl - 1x Abductor.stl - 1x Palm.stl - 1x Dorsal.stl Motors and Electronics: - 5x Pololu Micro Metal Gearmotor 1000:1 HP with extended motor shaft - 5x DRV8838 Single Brushed DC Motor Driver Carrier - 5x Pololu magnetic encoder for Micro Metal Geromotors - 1x Turnigy TGY-EX5252MG Twin BB Digital Micro Servo - 1x Teensy 3.1 Other Components: - 1x Fishing line spool (0.6 mm max. diameter) - 14x Small rubber bands (orthodontic elastic bands) - 14x M3x14 screw - 10x M3x8 screw - 2x M3x12 screw - 2x M3x12 spacer - 26x M3 nut