University of Washington engineers built a 1.0-gram hopping robot, DirectHop, that varies its jump height by controlling motor current instead of releasing stored spring energy. In one tethered lab demonstration, the robot cleared a 17-centimeter step with a 45-degree ramp under its foot. In separate tests on a flat, rigid surface, it righted itself after landing in nine of 10 trials.
Most tiny jumpers store energy in a spring and release it in one burst. That can produce higher jumps, but makes smaller, measured hops harder to command. DirectHop takes a different route: a coreless electric motor winds a line around a pulley to lift itself, while a lightweight carbon-fiber linkage keeps the moving motor aligned over the robot's foot.
The motor accounts for about 820 milligrams of the robot's 1-gram mass. By regulating current through its coils, the researchers could control motor torque and therefore the push at takeoff. Measurements from five jumps at each current setting showed a near-linear relationship between current and jump height. With a pair of small feet that tilted the body and a low-current setting, the robot also made forward hops shorter than 5 millimeters.
After landing, the motor reverses and reels in a second line, pulling the heavy motor down toward the foot. That shift in mass and a curved roll cage help the body roll upright. The robot completed four hops in sequence before its power wires began to interfere.
In the authors' comparison table, some spring-driven robots jumped more than 20 times their body length, while DirectHop's peak was about five. Its distinction is combining adjustable height and self-righting at roughly the 1-gram scale.
DirectHop is still a laboratory prototype: power and control remain offboard, and it cannot steer or navigate. The next test is whether it can keep its jump control and recovery after carrying its own battery and guidance hardware.
Sources
- Hanquan Wang, Yash P. Talwekar and Sawyer B. Fuller, “DirectHop: A Direct-Drive Insect-Sized Robot that can Control Jump Height and Self-Right,” paper for IROS 2026
- University of Washington, DirectHop announcement, Sept. 23, 2026
- Lead image: Moshe Sipper, “Grasshopper preparing to jump,” Wikimedia Commons, CC BY 4.0. Illustrative image, not the DirectHop robot.
