Hopping robots could consume less energy

Robots could use a tenth of current power requirements by using a rather odd two-part jump.

Taking a short hop before a big jump – in what the team terms a ‘stutter jump’ – could allow spring-based ‘pogo-stick’ robots to be far more efficient.

“If we time things right, the robot can jump with a tenth of the power required to jump to the same height under other conditions,” says Daniel Goldman of the Georgia Institute of Technology.

“In the stutter jumps, we can move the mass at a lower frequency to get off the ground. We achieve the same takeoff velocity as a conventional jump, but it is developed over a longer period of time with much less power.”

Given that jumping’s such an important means of locomotion for animals, it’s of great interest to robotics engineers. The formula for the two-part jump was discovered by analyzing nearly 20,000 jumps made by a simple laboratory robot under a wide range of conditions.

The researchers expected to find that the optimal jumping frequency would be related to the resonant frequency of the spring and mass system, but this turned out not to be the case. Instead, it was frequencies above and below the resonance that provided optimal jumping – and additional analysis revealed 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,” says Goldman. “You really don’t have to move the mass rapidly to get a good jump.”

But because it requires longer to perform than a simple jump, 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,” says 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 then look at other surfaces to develop a better understanding of how exploration or rescue robots can hop across them.