Development of a novel compact hydraulic power unit for the exoskeleton robot

Xiaoping Ouyang, Shuo Ding, Boqian Fan, Perry Y. Li, Huayong Yang

Research output: Contribution to journalArticle

15 Scopus citations


Exoskeleton robots require powerful and lightweight power supplies. Because of its high power-to-mass ratio and fast response, hydraulic systems can meet the requirement for locomotion robots. In this paper, a novel compact hydraulic power unit (CHPU) is proposed. A two-stroke IC engine, with a rated power of 2.4 kW at 13,000 rpm, is used as the prime mover. The engine drives a high speed (10,000 rpm) piston pump to allow the engine to operate at high power. A spring loaded reservoir has been developed to prevent the pump intake from cavitation and contamination. The payload flow rate is indirectly estimated using the displacements of the actuator. A Ragone plot analysis shows that the CHPU can maintain a high specific power over a long duration. A dynamic model for the CHPU has been developed based upon simplified engine operating characteristics and a set of experimentally identified parameters. A prototype of the CHPU has been constructed with a rated power of 1.45 kW and a weight of 16.6 kg. Experimental testing of the prototype confirms the dynamic model and the output capacity of the CHPU.

Original languageEnglish (US)
Pages (from-to)68-75
Number of pages8
StatePublished - Sep 1 2016


  • Exoskeleton robot
  • High specific power
  • Hydraulic power unit
  • Model
  • Parameters identification

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