Hydraulically Actuated Quadruped - HyQ

HyQ is a fully torque-controlled Hydraulically actuated Quadruped robot (pronounced [hai-kju:]) developed in the Department of Advanced Robotics at the IIT. HyQ is designed to move over rough terrain and perform highly dynamic tasks such as jumping and running with different gaits (up to 3-4m/s). To achieve the required high joint speeds and torques, a combination of hydraulic cylinders and electric motors are actuating the robot’s 12 active joints.

Goals of the project are the investigation of various aspects of quadrupedal locomotion, adjustable compliance, energy efficiency, compact hydraulic actuation and onboard power systems.

System Overview

The following table lists the key specifications of the robot platform.

Dimensions (fully stretched legs)	1.0m x 0.5m x 0.98m (Length x Width x Height)
Weight	70kg (external hydraulic power supply), 90kg (onboard hydraulic power supply)
Number of active DOF	12 (8 hydraulic and 4 electric)
Actuator Types	Hydraulic cylinders (80mm stroke, 16mm bore) and DC brushless motors with harmonic gear
Joint range of motion	120°
Maximum torque (electric)	152Nm (torque limit of gear)
Maximum torque (hydraulic)	145Nm (peak torque at max. pressure of 16MPa)
Onboard sensors	High-resolution position and torque on each joint, cylinder chamber pressure, inertial measurement unit (IMU), hydraulic system
Onboard computer	PC104 Pentium, real-time Linux (Xenomai)
Control frequency	1 kHz

Figure 2 shows the CAD model of the robot and 2 pictures with different views of HyQ’s mechanical skeleton built in aerospace-grade aluminium alloy and stainless steel. The robot’s torso is built with a folded aluminium alloy sheet with internal walls to achieve high torsional robustness.

Figure 2: CAD model of HyQ with onboard hydraulic system (left) and pictures of the mechanical skeleton of HyQ (centre and right).

Leg Design

Each leg features three degrees of freedom (DOF), two in the hip (abduction/adduction and flexion/extension) and one in the knee (flexion/extension). The leg is built of a light-weight aerospace-grade aluminium alloy and stainless steel. High resolution encoders and load cells in each joint allow a smooth control of both position and torque. We are currently designing and testing several foot designs with and without adjustable stiffness to soften the impacts at foot touch-down and to store energy from one step to the next.

Figure 3: Leg Design Evolution: CAD model and picture of HyQ leg prototype (left) and the improved final leg (right)

In the beginning of 2008, we successfully reached the first milestone of the project: The design and construction of a first 2-DOF leg prototype (Fig. 3, left) with an actuated hip and knee joint in the sagittal plane (Semini et al., 2008). Since then, we have extensively used the leg to test its mechanical structure, the hydraulic actuation system and to evaluate various joint level controllers (Semini et al, 2008; Cunha et al, 2009; Focchi et al, 2010). For the experiments the leg was either mounted to a vertical slider or fixed to a work bench. We studied the behavior of the mechanical structure and hydraulics upon leg impact with varying leg weights up to 25kg. Furthermore, we tested the leg during continuous hopping with different frequencies up to 3Hz, since hopping is a simplified form of running (see video).

The experiments proofed that hydraulic actuation is very suitable for highly dynamic legged robots, due to its high power-to-weight ratio, high torque and speed and ability to cope with torque peaks (Semini, 2010).

Coming next

System testing and first walking/running experiments on a treadmill.
Study of Locomotion with a focus on rough terrain walking and balancing.
Study of highly dynamic motions (e.g. jumping and running trot with 3-4m/s)
Study of energy efficient locomotion (e.g. evaluation of different foot designs with/without adjustable stiffness and/or damping).
Development and evaluation of compact and energy-efficient hydraulic components (Guglielmino et al, 2009).
Investigation of water hydraulic actuation systems for robotics
Power-autonomous version of HyQ.

List of Publications

Dissertations

2010

C. Semini, "HyQ – Design and Development of a Hydraulically Actuated Quadruped Robot,” Dissertation, Italian Institute of Technology and University of Genoa, Italy, 2010.
[full thesis]
BibTeX

@PHDTHESIS{semini10PhDthesis,
author = {Claudio Semini},
title = {{HyQ -} Design and Development of a Hydraulically Actuated Quadruped Robot},
school = {Italian Institute of Technology and University of Genoa},
year = {2010},
timestamp = {2010.09.12}}

Journal, Conference Papers and Posters

2012

T. Boaventura, C. Semini, J. Buchli, M. Frigerio, M. Focchi, D. G. Caldwell, "Dynamic Torque Control of a Hydraulic Quadruped Robot", Proceedings IEEE International Conference on Robotics and Automation (ICRA), 2012, St. Paul, USA. [accepted for publication].
[full article]
BibTeX

@INPROCEEDINGS{Boaventura2012ICRA
author = {T. Boaventura and C. Semini and J. Buchli and M. Frigerio and M. Focchi and D.G. Caldwell},
title = {Dynamic Torque Control of a Hydraulic Quadruped Robot},
booktitle = {Proceedings IEEE International Conference on Robotics and Automation (ICRA)},
year = {2012},
note = {[Submitted]},
owner = {phd},
timestamp = {2011.11.25}}

S. Peng, D. T. Branson, E. Guglielmino, T. Boaventura, and D. G. Caldwell, "Performance Assessment of Digital Hydraulics in a Quadruped Robot Leg", Proceedings of the 11th Biennial Conference on Engineering Systems Design and Analysis ESDA11, 2012.

2011

T. Boaventura, C. Semini, J. Buchli, D. G. Caldwell, "Actively-compliant leg for dynamic locomotion", Proceedings 5th International Symposium in Adaptive Motion of Animals and Machines (AMAM), 2011, Hyogo, Japan.
[full article]
BibTeX

@CONFERENCE{Boaventura11Amam,
author = {Boaventura, Thiago and Semini, Claudio and Buchli, Jonas and Caldwell, Darwin G.},
title = {Actively-compliant Leg for Dynamic Locomotion},
booktitle = {Int. Symp. Adaptive Motion in Animals and Machines (AMAM)},
year = {2011},
timestamp = {2011.09.15}}

M. Frigerio, J. Buchli and D. G. Caldwell, "A Domain Specific Language for kinematic models and fast implementations of robot dynamics algorithms", 2nd International Workshop on Domain-Specific Languages and models for ROBotic systems (DSLRob’11), San Francisco, September 2011.
[full article]
BibTeX

@INPROCEEDINGS{frigerio:2011:kindsl,
author = {Marco Frigerio and Jonas Buchli and Darwin G. Caldwell},
title = {A Domain Specific Language for kinematic models and fast implementations of robot dynamics algorithms},
booktitle = {2nd International Workshop on Domain-Specific Languages and models for ROBotic systems (DSLRob)},
year = {2011},
month = {September},
keywords = {DSL, software, kinematics, dynamics, code generation, real time}}

C. Semini, N. G. Tsagarakis, E. Guglielmino, M. Focchi, F. Cannella, and D. G. Caldwell, “Design of HyQ - a hydraulically and electrically actuated quadruped robot,” IMechE Part I: J. of Systems and Control Engineering, vol. 225, no. 6, pp. 831–849, 2011.
[full article]
BibTeX

@ARTICLE{Semini11HyQdesignJSCE,
   author = {Semini, Claudio and Tsagarakis, Nikos G. and Guglielmino, Emanuele
        and Focchi, Michele and Cannella, Ferdinando and Caldwell, Darwin G.},
   title = {Design of {HyQ} - a Hydraulically and Electrically Actuated Quadruped Robot},
   journal = {IMechE Part I: J. of Systems and Control Engineering},
   year = {2011},
   volume = {225},
   pages = {831-849},
   number = {6},
   owner = {CSemini},
   timestamp = {2011.02.20}}

C. Semini, J. Buchli, M. Frigerio, T. Boaventura, M. Focchi, E. Guglielmino, F. Cannella, N. G. Tsagarakis, and D. G. Caldwell, “HyQ – a dynamic locomotion research platform,” in Int.l Workshop on Bio-Inspired Robots, Nantes (France), 2011.
     [full article] [{yootooltip title=[BibTex citation] sticky=[1]}
@CONFERENCE{Semini11BioInspNantes,
   author = {Semini, Claudio and Buchli, Jonas and Frigerio, Marco and Boaventura,
        Thiago and Focchi, Michele and Guglielmino, Emanuele and Cannella,
        Ferdinando and Tsagarakis, Nikos G. and Caldwell, Darwin G.},
   title = {{HyQ} -- A Dynamic Locomotion Research Platform},
   booktitle = {Int.l Workshop on Bio-Inspired Robots, Nantes (France)},
   year = {2011},
   owner = {csemini},
   timestamp = {2011.09.16}
}
{/yootooltip}]

2010

M. Focchi, E. Guglielmino, C. Semini, T. Boaventura, Y. S. Yang, D. G. Caldwell, "Control of a Hydraulically-Actuated Quadruped Robot Leg," IEEE Int. Conf. on Robotics and Automation (ICRA), 2010.
Semini, C. and Tsagarakis, N.G. and Guglielmino, E. and Caldwell, D.G., Design and experimental evaluation of the hydraulically actuated prototype leg of the HyQ robot, International Conference on Intelligent Robots and Systems (IROS), 2010 IEEE/RSJ.
[full article] [{yootooltip title=[BibTex citation] sticky=[1]}
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author={Semini, C. and Tsagarakis, N.G. and Guglielmino, E. and
Caldwell, D.G.},
booktitle={Intelligent Robots and Systems (IROS), 2010 IEEE/RSJ
International Conference on},
title={Design and experimental evaluation of the hydraulically actuated
prototype leg of the HyQ robot},
year={2010},
month={oct.},
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number={},
pages={3640 -3645},
keywords={HyQ robot;cylinder force data;cylinder pressures;high impact
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redundancy;hydraulic actuators;legged locomotion;multi-robot systems;},
doi={10.1109/IROS.2010.5651548},
ISSN={2153-0858},}
{/yootooltip}]
C. Semini, N. Tsagarakis, E. Guglielmino, D. G. Caldwell, "Design of a Hydraulic Quadruped Robot," Workshop on Human Adaptive Mechatronics (HAM), 2010.

2009

Y. S. Yang, C. Semini, E. Guglielmino, N. G. Tsagarakis, D. G. Caldwell, "Water vs. Oil Hydraulic Actuation for a Robot Leg," IEEE Int. Conf. on Mechatronics and Automation (ICMA), pp. 1940-1946, 2009.
[full article] [{yootooltip title=[BibTex citation] sticky=[1]}
@INPROCEEDINGS{5246620,
author={Yousheng Yang and Semini, C. and Guglielmino, E. and Tsagarakis,
N.G. and Caldwell, D.G.},
booktitle={Mechatronics and Automation, 2009. ICMA 2009. International Conference on},
title={Water vs. oil hydraulic actuation for a robot leg},
year={2009},
month={aug.},
volume={},
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pages={1940 -1946},
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Y. S. Yang, C. Semini, N. G. Tsagarakis, E. Guglielmino, D. G. Caldwell, "Leg Mechanisms for Hydraulically Actuated Robots," IEEE/RSJ Int. Conf. on Intelligent RObots and Systems (IROS), pp. 4669-4675, 2009.
[full article] [{yootooltip title=[BibTex citation] sticky=[1]}
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title={Leg mechanisms for hydraulically actuated robots},
year={2009},
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keywords={actuator chambers;highly dynamic robotic machines;hydraulic
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E. Guglielmino, C. Semini, Y. S. Yang, D. G. Caldwell, H. Kogler, R. Scheidl, "Energy Efficient Fluid Power in Autonomous Legged Robotics," ASME Dynamic Systems and Control Conference (DSCC), 2009.
[full article]
T. B. Cunha, C. Semini, E. Guglielmino, V. J. De Negri, Y. S. Yang, D. G. Caldwell, "Gain Scheduling Control for the Hydraulic Actuation of the HyQ Robot Leg," Int. Conf. of Mechanical Engineering (COBEM), 2009.

2008

C. Semini, N. G. Tsagarakis, B. Vanderborght, Y. S. Yang and D. G. Caldwell, "HyQ - Hydraulically Actuated Quadruped Robot: Hopping Leg Prototype," IEEE/RAS-EMBS Int. Conf. on Biomedical Robotics and Biomechatronics (BioRob), pp.593-599, 2008.
[full article] [{yootooltip title=[BibTex citation] sticky=[1]}
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author={Semini, C. and Tsagarakis, N.G. and Vanderborght, B. and
Yousheng Yang and Caldwell, D.G.},
booktitle={Biomedical Robotics and Biomechatronics, 2008. BioRob 2008.
2nd IEEE RAS EMBS International Conference on},
title={HyQ - Hydraulically actuated quadruped robot: Hopping leg prototype},
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{/yootooltip}]
C. Semini, N. G. Tsagarakis, D. G. Caldwell, "Dynamic Tasks of a Hydraulically Actuated Quadruped Robot," Poster at Dynamic Walking Conference, Delft (The Netherlands), May 2008.
[poster]
C. Semini, N. G. Tsagarakis, D. G. Caldwell, "Bio-Inspired Design of a Hydraulically Actuated Quadruped Robot [HyQ]," Poster at Robotics: Science and Systems (RSS) Conference, Zurich (Switzerland), June 2008.
Y. S. Yang, C. Semini, N. G. Tsagarakis, D. G. Caldwell, Y. Zhu, "Water hydraulics - A novel design of spool-type valves for enhanced dynamic performance," IEEE/ASME Int. Conf. on Advanced Intelligent Mechatronics (AIM), pp. 1308-1314, 2008.
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title={Water hydraulics - A novel design of spool-type valves for enhanced dynamic performance},
year={2008},
month={july},
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