In order to enable a humanoid robot to perform acrobatic motions like backflips, spins, or jumps, complex hardware design, planning, and control algorithms have to be introduced. A recent paper on arXiv.org proposes the MIT Humanoid robot that can perform highly dynamic motions.
MIT Humanoid Backflip. Image credit: Matthew Chignoli et al, arXiv:2104.09025
The robot relies on the design of previous MIT Cheetah robots. Two new actuators are developed to satisfy the torque and power requirement for impulsive behaviors. On the software side, a new torque limit constraint is introduced into the kino-dynamic planner.
The stable landing is achieved by integrating two previously used control methods. A novel dynamics simulator lets to choose the optimal trajectories. Different motions such as aerial flips and spins are demonstrated in simulations. The experiments show that the demonstrations are feasible and ready for hardware implementation.
Demonstrating acrobatic behavior of a humanoid robot such as flips and spinning jumps requires systematic approaches across hardware design, motion planning, and control. In this paper, we present a new humanoid robot design, an actuator-aware kino-dynamic motion planner, and a landing controller as part of a practical system design for highly dynamic motion control of the humanoid robot. To achieve the impulsive motions, we develop two new proprioceptive actuators and experimentally evaluate their performance using our custom-designed dynamometer. The actuator’s torque, velocity, and power limits are reflected in our kino-dynamic motion planner by approximating the configuration-dependent reaction force limits and in our dynamics simulator by including actuator dynamics along with the robot’s full-body dynamics. For the landing control, we effectively integrate model-predictive control and whole-body impulse control by connecting them in a dynamically consistent way to accomplish both the long-time horizon optimal control and high-bandwidth full-body dynamics-based feedback. Actuators’ torque output over the entire motion are validated based on the velocity-torque model including battery voltage droop and back-EMF voltage. With the carefully designed hardware and control framework, we successfully demonstrate dynamic behaviors such as back flips, front flips, and spinning jumps in our realistic dynamics simulation.
Research paper: Chignoli, M., Kim, D., Stanger-Jones, E., and Kim, S., “The MIT Humanoid Robot: Design, Motion Planning, and Control For Acrobatic Behaviors”, 2021. Link: https://arxiv.org/abs/2104.09025