"Stutter jump" could improve performance of search and rescue robots

pattern of movement and the frequency of movement applied by an actuator built into the robot’s mass. A high-speed camera and a contact sensor measured and recorded the height of each jump.

See this Web site for how changes affect jumping.

Aguilar and Goldman then collaborated with theorists Professor Kurt Wiesenfeld and Alex Lesov, from the Georgia Tech School of Physics, to explain the results of the experiments.

The researchers expected to find that the optimal jumping frequency would be related to the resonant frequency of the spring and mass system, but that turned out not to be true. Detailed evaluation of the jumps showed that frequencies above and below the resonance provided optimal jumping — and additional analysis revealed what the researchers called the “stutter jump.”

“The preparatory hop allows the robot to time things such that it can use a lower energy to get to the same jump height,” Goldman explained. “You really don’t have to move the mass rapidly to get a good jump.”

The amount of energy that can be stored in batteries can limit the range and duration of robotic missions, so the stutter jump could be helpful for small robots that have limited power.

Optimizing the efficiency of jumping could therefore allow the robots to complete longer and more complex missions.

Because it requires longer to perform than a simple jump, however, the two-step jump may not be suitable for all conditions.

“If you’re a small robot and you want to jump over an obstacle, you could save energy by using the stutter jump even though that would take longer,” said Goldman. “But if a hazard is threatening, you may need to expend the additional energy to make a quick jump to get out of the way.”

For the future, Goldman and his research team plan to study how complicated surfaces affect jumping. They are currently studying the effects of sand, and will turn to other substrates to develop a better understanding of how exploration or rescue robots can hop through them.

Goldman’s past work has focused on the lessons learned from the locomotion of biological systems, so the team is also interested in what the robot can teach them about how animals jump. “What we have learned here can function as a hypothesis for biological systems, but it may not explain everything,” he said.

The simple jumping robot turned out to be a useful system to study, not only because of the interesting behaviors that turned up, but also because the results were counter to what the researchers had expected.

“In physics, we often study the steady-state solution,” Goldman noted. “If we wait enough time for the transient phenomena to die off, then we can study what’s left. It turns out that in this system, we really care about the transients.”

— Read more in Jeffrey Aguilar  et al., “Lift-Off Dynamics in a Simple Jumping Robot,” Physical Review Letters 109, no. 17 (26 October 2012) (DOI: 10.1103/PhysRevLett.109.174301)