Multifunctional One-Legged Jumping Robot Breaks Walking Limitations on Sand and Ice

Engineers at the University of Toronto have designed a flexible footpad for a one-legged jumping robot, enabling it to navigate sand, ice, and other challenging terrains. The robot, named Hopcopter, is essentially a quadcopter mounted on a large spring-loaded foot. The research team aims to apply it in search and rescue operations, remote infrastructure inspections, and even interplanetary exploration. The related research findings were published in Advanced Intelligent Systems, with Professor Pakpong Chirarattananon from the Department of Mechanical and Industrial Engineering as the lead author.

Chirarattananon stated that drones are inexpensive, capable of flying over various terrains, and excel in photography and videography. However, due to the need for lightweight designs, the cargo capacity of drones is limited, and their range is constrained by the amount of fuel they can carry. In contrast, wheeled and legged robots can carry more cargo and travel farther, but they tend to be more expensive and may not handle rugged terrains effectively. He believes there is room for a new type of robot that bridges the gap between the two. His lab, called the "Convergent Motion, Intelligent Mechanisms, and Bio-inspired Robotics Laboratory" (CLIMB), draws inspiration from nature to balance range, efficiency, cost, and cargo capacity.

The design of Hopcopter is inspired by birds, which do not continuously fly but instead soar between different locations, resting for extended periods and sometimes jumping on the ground. PhD student Song Li from City University of Hong Kong played a significant role in the robot's development during an academic exchange in Toronto. The long legs of Hopcopter raise its center of gravity above the ground, while pre-tensioned rubber bands counteract gravity and other forces. Lead author and PhD student in Mechanical and Industrial Engineering Jeeraphat (Owen) Kledkruemas noted that this makes the robot easier to model and control compared to other jumping robots.

The jumping capability allows the robot to overcome obstacles that most wheeled or legged robots cannot, while conserving energy and carrying more weight than standard drones.

Challenges and Solutions in Footpad Design

The original Hopcopter performed well on flat concrete or fine gravel but faced challenges on other surfaces. If it lands at a steep angle or on slippery surfaces like ice, the robot's foot can slide, causing it to lose balance. On sand or other soft surfaces, the foot can sink and become stuck. Kledkruemas designed the footpad to distribute the robot's weight over a larger area, similar to how snowshoes prevent the wearer from sinking into snow. Spherical joints allow the footpad to tilt with the ground, and rubber bands automatically restore its position after each jump.

The bottom of the footpad is covered with short spikes to enhance grip, similar to the crampons used by ice climbers.

Future Applications and Challenges

According to the researchers, the newly designed footpad has reduced takeoff errors by up to 66% and improved efficiency by as much as 64%. Additionally, the footpad has narrowed performance variability across different terrains by 84%, making Hopcopter's performance on difficult ground nearly equivalent to that on smooth surfaces. Kledkruemas noted that these improvements make jumping on ice and sand possible.

The team plans to develop an autonomous navigation system for Hopcopter and tackle greater challenges. Chirarattananon stated that this improvement enables them to "bring this robot from the lab into the real world." He envisions using it for search and rescue operations after natural disasters or inspecting remote infrastructures like pipelines and mines. The team also dreams of exploring places like Mars, where the atmosphere is too thin for most types of drones.

Potential Applications of New Robot Technology

The design of Hopcopter breaks the limitations of traditional drones and robots, particularly in addressing complex terrains. Its innovative footpad design not only enhances the robot's stability but also expands its range of applications, from search and rescue to remote infrastructure inspections and even planetary exploration. The development of this technology could change how robots operate in various environments in the future, especially in rescue operations following natural disasters, providing more effective solutions.