The Right Move: How Domin Servo Valves Enable Agile Quadruped Robots

Quadruped Robot Hydraulics

Quadruped robots like Boston Dynamics’ Spot are gaining popularity for applications like package delivery, inspection, search and rescue, and entertainment. With their animal-like legged mobility, quadrupeds can nimbly traverse uneven terrain that would stop wheeled robots in their tracks.

Hydraulic actuators are a key enabling technology for high-performance quadrupeds. Compared to electrics, hydraulics provides higher power density and shock tolerance in a compact, lightweight package. This allows each leg to lift heavy loads and absorb impacts from jumping and running. Precisely controlling those hydraulic joints is critical for robots to walk, trot, and bound. Without responsive valves, gaits become unstable. Domin S4 Pro electro-hydraulic servo valves provide the speed and accuracy needed for agile quadruped robots.

Researchers at Zhejiang and Nanchang Universities built a hydraulic quadruped prototype to evaluate control algorithms. However, smoothly controlling the many hydraulic leg joints proved challenging. This case study explores how Domin S4 Pro servo valves provided the precision and speed needed for their agile quadruped robot.

The Quadruped Robot Challenge

The university researchers’ quadruped mimics animal movement with four legs, providing better mobility than wheels over rocky, angled, or sandy terrain. However, controlling the many actively articulating joints is complex. Each leg must precisely cycle through different configurations to walk, trot, gallop, or bound. Missteps risk instability.

The hydraulic leg actuators that enable quadruped mobility also presents a control challenge. Valves must quickly and accurately coordinate multiple joints to maintain stability through dynamic motions. Slow or imprecise valves lead to wobbly, inefficient gaits. This demands servo valves with high bandwidth, fast response, and compact footprint to fit in legs.

Domin S4 Pro Benefits


Weighing just 250g, Domin S4 Pro valves minimize mass on moving legs. This allows faster cycling and more dynamic motion.

High Bandwidth

With bandwidth over 120 Hz, S4 Pro valves offer incredibly responsive control. Legs react quicker to maintain stability.

Power Density

A compact but powerful valve, the S4 Pro provides 12 L/min flow in a small package. Legs generate more force for their size.

Fast Response

Short 3ms response time enables precise movements. Legs can make fine adjustments to handle uneven terrain.

Precision Control

Superior servo performance lets quadrupeds achieve complex, stable gaits. S4 Pro valves command legs for accurate trajectories.

S4 Pro

Real-World Results: Hydraulic Quadruped Robot Project

To evaluate quadruped control algorithms, the researchers at Zhejiang and Nanchang Universities built a hydraulic robot leg testbed. The single-leg prototype has 3 degrees of freedom just like a quadruped’s limbs.

They selected Domin S4 Pro valves to actuate the leg’s hip and knee joints due to the valves’ optimal blend of speed, precision, and small footprint. The valves connect to a custom control board that precisely coordinates them based on feedback from pressure sensors and encoders.

In testing, this S4 Pro motion control system enabled the leg to track target joint trajectories within 5 degrees of accuracy. This level of precision provides the stable, programmable gaits over uneven terrain that quadrupeds need.

Contact Domin

As quadrupeds progress from controlled labs to unpredictable real-world use, responsive and compact servo valves will only grow in criticality. With unmatched bandwidth, precision, and power density, Domin’s S4 Pro is the ideal choice for enabling next-generation hydraulic quadrupeds and humanoids.

To discuss leveraging Domin’s expertise in quadruped robotics and motion control, contact us today. More details on the university research project are available on Science Direct.