There are numerous, some ways to use mechanical benefit to the output of an electrical motor to realize desired speeds, torque, and precision. All of them have each benefits and drawbacks, however related robots are likely to have related wants. That’s why we see plenty of robotic actuators with planetary gearboxes, cycloidal drives, and harmonic (pressure wave) gearing. However although the “good” system hasn’t been discovered, as a result of it might’t truly exist, Aaed Musa’s capstan drives are very interesting and to show it, he constructed a robotic canine referred to as CARA.
The time period “capstan drive” refers to its resemblance to the capstans you see on ships. The fundamental thought is that the rotating electrical motor winds a rope or cable come what may, which forces the output shaft to rotate accordingly. However the ratio of the motor’s spool diameter and the output shaft’s pulley diameter may be very totally different, leading to a gear discount. Capstan drives have a number of benefits, together with low value, unfastened fabrication tolerances, easy and quiet operation, little or no backlash, and simple meeting.
And in case you google “capstan drive,” the primary end result you’ll see is Musa’s web site. That’s as a result of he has been a pioneer within the growth of maker-friendly capstan drives and has completed greater than anybody else to convey them to the eye of novice and even skilled roboticists.
CARA, which stands for “Capstans Are Actually Superior,” cements Musa’s fame on this house. CARA is a robotic canine with 12 actuated joints, every with its personal 3D-printed capstan drive powered by an Eaglepower 90KV brushless DC motor. They’ve 8:1 reductions and are pushed by ODrive S1 controllers with magnetic encoders.
A Teensy 4.1 microcontroller growth boards sends instructions to the ODrive S1 controllers by a CAN bus utilizing an SN65HVD230-based Waveshare transceiver. The Teensy, in flip, receives motion instructions from a primary Radiolink eight-channel radio transmitter and receiver set. A Sparkfun BNO086 IMU helps CARA sense its personal orientation, relative to the Earth. Energy comes from a 24V 3000mAh battery, which Musa says might be too small for the applying. However it’s what he had readily available.
With that {hardware}, Musa was then in a position to develop strolling gaits for CARA. As a result of every leg has three actuated joints, Musa had fairly a little bit of freedom to experiment and discover an optimum gait.
The ensuing motion may be very spectacular. CARA can stroll with plenty of grace, compensate for surfaces with a excessive grade, and even soar — a feat that has develop into a necessity for displaying off within the robotics world.
If you wish to attempt Musa’s capstan drive design your self, you possibly can get the recordsdata by his Patreon — both by turning into a member or buying the recordsdata straight.
