Jumping Mynock
Course - ME112 - Mechanical Systems Design
Duration - 1 month, March 2018
Materials - plywood, springs, fasteners, Tamiya gearbox kit, 9V battery
Our objective was to build a robonock (robot mynock, inspired by Star Wars) which jumped vertically and stuck to a surface 1 meter above the ground. The robonock had to complete the jump autonomously using its own power supply and within 5 seconds of starting the motor.
We drew inspiration from the jumping motions of fleas and frogs for our design. Our robot body was based on a flea-like collapsing rhombus which started short and wide and ended tall and thin. A set of springs generated a moment about two of the links which produced the jumping motion. Our robot's release mechanism was inspired by a frog, which stores and releases energy in a tendon via a passive mechanism. This design restricted the springs from producing a moment about the joint until sufficient energy was stored to propel the robonock to the full meter. Thus, the launch was spontaneous, and the robot did not rely on an additional release mechanism.
Four-bar linkage
Mynock in flight
The design used a speed reducing gear ratio of 196.7:1, and was made out of airplane-grade plywood to minimize weight. The robonock drew 4.05J from a 9V battery each jump.
On Demonstration Day, our robot successfully ascended the full meter and jumped autonomously within 4.5 seconds after powering the motor. This was the second-fastest time in the class, among robots that cleared the full meter.
Lego Crawler
Final crawler design
Underside of crawler, revealing transmission
Course - ME112 - Mechanical Systems Design
Duration - 1 month, February 2018
Materials - LEGOs, Duron, motor, rubber bands
The goal of this project was to design a small, LEGO vehicle that could travel through a 2-meter tunnel lined with gravel, retrieve a plastic salamander, and return to the entrance of the tunnel with the salamander — all without expending more than 10J of energy.
Our final design was the Supermander: a four-wheel drive car that used a gear ratio of 1:45. Four-wheel drive allowed the car to navigate bumps when moving forwards and backwards. The 1:45 gear ratio closely aligned with the optimum motor efficiency (50%). To retrieve the salamander, we created a bumper at the front of the car covered with VHB Tape. When the bumper hit salamander, the target firmly stuck to the tape as the vehicle dragged it back to the entrance. Testing revealed this design to be a simple yet reliable system that could be tested repeatedly with little setup time required.
On Demonstration Day, our vehicle successfully retrieved the salamander. The car expended 6.4J of energy, which was within the 10J threshold. The vehicle's overall efficiency was 11%. Future iterations will require further optimization of our transmission and motor. Energy was also lost due to rolling, slippage, and non-linear motion.
