We demonstrate a jumping robot that reaches high (7.6 m) and fast (190 ms stance time) jumps from a single long leg driven by a direct-drive transmission, without elastic energy storage. At 281 g, it achieves the highest jump yet reported for an electrically actuated, spring-free system. The leg uses a new fabric-wrap transmission that provides a variable mechanical advantage, keeping a small electric motor near its peak power output through the stroke while bracing the long, lightweight leg against buckling. A balancing module at the top of the leg uses small propellers to control the leg's orientation on the ground and in the air, where the long leg provides a large moment arm for the control torques. The robot is validated outdoors with vertical jumps, attitude control on the ground and in flight, and tilted jumps.
Figures & tables
Fig. 1: Overlay of a single vertical jump, composited from frames 166.7ms apart, with a person of height 1.83m for scale.
Fig. 2: Overview of the robot and its three subsystems: the body, the balancing module, and the leg. (a) The full robot, with a leg stroke of 1867mm and a body height of 83mm . (b) The balancing module, mounted at the top of the leg. (c) The body, containing the main actuator.
Fig. 3: Actuation strategies, each drawn as a rack and pinion. The colored part is the actuated element, the rack is the leg, and the red arrow marks the actuator output. (a) Series-elastic (SE) actuation: elastic element in series. (b) Parallel-elastic (PE) actuation: elastic element in parallel, with a latch. (c) Direct-drive (DD) actuation: rigid coupling, no elastic element.
Type
Reference
Mass
Leg stroke
Jump height
VJA
( kg )
( cm )
( m )
( ms−1 )
DD
This work
0.28
187
7.6
5.30
Wagner and Yim [ 8 ]
1.25
20
0.59
1.19
Suzuki et al. [ 28 ]
10.3
80
1.6
2.00
Kau et al. [ 23 ]
4.8
16
1.14
2.23
Park et al. [ 25 , 26 , 27 ]
33
80
0.5
1.11
TABLE I: Comparison of Electrically Actuated Jumping Robots
Subsystem
Component
Mass ( g )
Body
Motor
53
Battery
88
Chassis, electronics, wiring
51
Subtotal
192
Balancing module
Motors ( 4× )
12
Batteries ( 2× )
14
TABLE II: System Mass Breakdown
Fig. 4: Schematic of the fabric-wrap transmission principle. (a) The fabric spirals around the leg at a spiral wrap angle ϕ , converting motor torque τ into tension T and the vertical ground reaction force (GRF) that drives the motion x along the leg. (b) At the start of stance, the fabric wraps at radius r0 . (c) As the leg extends, the radius grows to r(x) , decreasing the mechanical advantage (MA). (d) A rack and pinion [ 8 ] , by contrast, keeps r fixed, causing a constant mechanical advantage.
Fig. 5: Attitude-control model. L is the length from foot to the balancing module, F is the net thrust at the module, and ψ is the lean from vertical. (a) Contact phase: the system is an inverted pendulum about the foot, with the body center of mass at x0 and a tripod contacting the ground for support. (b) Aerial phase: the system rotates about its center of mass at xCOM , with the body at x .
Fig. 6: Top-down layout of the vertical jump test setup, showing the placements of the two GoPro cameras, the meter stick length references, and the robot.
Fig. 7: Body displacement during a single vertical jump, reconstructed by stereo triangulation. ΔZ is the vertical component; ΔX and ΔY are horizontal. The body reached a peak height of 7.6m .
Fig. 8: Main actuator telemetry during the jump: winding current, motor shaft velocity, bus voltage, and mechanical power. After an initial ramp, the power holds near its peak for the rest of the stroke.
Fig. 9: On-ground attitude control. (a) Overlay of the robot setting a pitch lean angle. (b) Commanded (dashed) and measured (solid) roll and pitch, with the thruster duty cycle below.
Fig. 10: Roll and pitch telemetry of the balancing module during a vertical jump (top); the gray region marks the post-liftoff phase. The controller switches from ground to aerial gains after liftoff. The bottom plot shows the thruster duty cycle.
Fig. 11: Tilted jump. (a) Overlay of the lean and jump, with frames 166.7ms apart after liftoff; the reference stick on the ground is 1m long. (b) Snapshot sequence of the stance and liftoff phase at 20.8ms intervals.
Fig. 12: Balancing-module telemetry (top): solid lines are measured values, dashed lines are setpoints. The robot balances, tilts, and then jumps. The bottom plot shows the body speed following the jump command issued at 0s ; the robot lifts off at approximately 190ms .
We present a rolling and jumping underactuated monopedal robot designed to explore multimodal locomotion on low-gravity bodies. It uses only two reaction wheels to control its spatial orientation with two controllers: a balancing controller which can aim the robot's jump direction on the ground, and an aerial reorientation controller which can aim the robot's leg for landing after flight. We demonstrate rolling, targeted jumping and landing, and self-righting using only three actuators total, keeping system size to 0.33m and 1.25kg. Simple switching between locomotion modes enables the system to deal with differing landscapes and environmental conditions.
Neil R. Wagner, Justin K. Yim
Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign
Quadrupedal wheeled-legged robots combine the advantages of legged and wheeled locomotion to achieve superior mobility, but executing dynamic jumps remains a significant challenge due to the additional degrees of freedom introduced by wheeled legs. This paper develops a mini-sized wheeled-legged robot for agile motion and presents a novel motion control framework that integrates the Nonlinear Model Predictive Control (NMPC) for locomotion and the Differential Evolution (DE) based trajectory optimization for jumping in quadrupedal wheeled-legged robots. The proposed controller utilizes wheel motion and locomotion to enhance jumping performance, achieving versatile maneuvers such as vertical jumping, forward jumping, and backflips. Extensive simulations and real-world experiments validate the effectiveness of the framework, demonstrating a forward jump over a 0.12 m obstacle and a vertical jump reaching 0.5 m.
Xuanqi Zeng, Lingwei Zhang, Linzhu Yue +4
Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong
Quadruped robots are becoming increasingly essential for various applications, including industrial inspection and catastrophe search and rescue. These scenarios require robots to possess enhanced agility and obstacle-navigation skills. Nonetheless, the performance of current platforms is often constrained by insufficient peak motor power, limiting their ability to perform explosive jumps. To address this challenge, this paper proposes a bio-inspired method that emulates the energy-storage mechanism found in froghopper legs. We designed a Deployable Compliant Leg (DCL) utilizing a specialized 3D-printed elastic material, Polyether block amide (PEBA), featuring a lightweight internal lattice structure. This structure functions analogously to biological tendons, storing elastic energy during the robot's squatting phase and rapidly releasing it to augment motor output during the leap. The proposed mechanical design significantly enhances the robot's vertical jumping capability. Through finite element analysis (FEA) and experimental validation, we demonstrate a relative performance improvement of 17.1% in vertical jumping height.
Yiyang Chen, Yuxin Liu, Jinzheng Zhou +4
Department of Mechatronics and Robotics, Xi’an Jiaotong-Liverpool University, Suzhou 215123, China. · Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois, United States.