Design of an Integrated Pneumatic-Electromagnetic Hybrid Linear...
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Design of an Integrated Pneumatic-Electromagnetic Hybrid Linear Actuator Yoshihiro Nakata 1 , Tomoyuki Noda 2 , Jun Morimoto 2 and Hiroshi Ishiguro 1 Abstract—We propose a compact direct-drive hybrid actu- ator with pneumatic-electromagnetic integrated structure. In this hybrid actuator, pneumatic and electromagnetic actuator components are perfectly integrated into a compact body. The actuator can realize both high bandwidth frequency control and high power weight ratio. Concept and design of this actuator are described. I. INTRODUCTION Development of mechanisms for humanoid and exoskele- ton robots to realize safe human-robot interaction is an im- portant issue of robotics. High bandwidth variable impedance and high power/weight ratio actuator is crucial for such kind of applications. However, every actuator with single actuation principle has some drawbacks and advantages, and hybrid actuators are getting a lot more attention lately [1], [2]. Noda et al. proposed a pneumatic-electric (P-E) hybrid ac- tuator [3] considering an optimal torque distribution method for their exoskeleton robot named “XoR” [4]. Output force of the actuator is generated by an antagonistic pair of pneumatic artificial muscles and a DC servomotor. However, previous hybrid actuators were made just connecting two types of actuators via mechanical parts e.g. link, timing belt and gear. Because of this, they tend to become large and fragile due to their complicated structures. To solve this problem, we proposed an integrated pneumatic-electromagnetic hybrid linear actuator (IPEHLA). This actuator has an efficiently shared architecture in terms of volume space and force transmission. The pneumatic and the electromagnetic actuator components share the stator (cylinder) and the mover (piston), and there is no connection mechanism between them. Force of this actuator can be 10 times as large as one of single electromagnetic linear actuator with same volume. II. PROPOSED HYBRID LINEAR ACTUATOR The cross-sectional view of proposed hybrid linear ac- tuator is shown in Fig. 1 (iii). Pneumatic and electromag- netic actuators are perfectly integrated into a compact body. The stator and the mover of the electromagnetic actuator component work as cylinder and piston of the pneumatic actuator component, respectively, and potentially provide the capability to exploit both advantages of these components. *This work was supported by MEXT/JSPS KAKENHI (#26540134, #24700203 and #26700026). 1 Department of Systems Innovation, Graduate School of Engineering Science, Osaka University, Osaka, Japan {nakata, ishiguro}@is.sys.es.osaka-u.ac.jp 2 Department of Brain Robot Interface, ATR Computational Neuroscience Laboratories, Kyoto, Japan {t noda, xmorimo}@atr.jp Servo-valve Coil Permanent magnet Air chamber Air chamber Magnetic core Air sealing plate Backyoke Servo-valve Driving direction Magnetization direction Foot Knee Hip (i) Robots with EMLAs (ii) Linear vernier motor (iii) Integrated pneumatic-electromagnetic hybrid linear actuator Air chamber Air chamber Fig. 1. Robotic arm with EMLAs, LVM and CAD model of IPEHLA Thus, no connection mechanism between two actuators is necessary. Nakata et al. have been studying a direct- drive electromagnetic linear actuator (EMLA) which can control the output force by quick changes of exiting coil current and enables robots’ joint to have active visco-elastic characteristics [5] (See Fig. 1 (i)). Furthermore, a linear vernier motor (LVM) with high force density employing magnetic gearing effect has been proposed [6] (See Fig. 1 (ii)). These electromagnetic structure can be applied to the hybrid actuator and improve the output force and response characteristics. The stator is composed of a back yoke, sets of 3-phase coils and 2 air vents at each end connecting to servo-valves. The back yoke works as magnetic shielding and a leakage of magnetic flux to outside the actuator is negligibly small. The mover is composed of sets of ring-shaped permanent magnets (NdFeB) between magnetic cores and an air sealing plate at one end. Axially opposite magnetized magnets are alternatively arranged. Thanks to this structure, high magnetic flux can be generated, especially the effective radial component of flux with an inward and outward direction from the magnetic cores. Output force is broadly controlled by compressed air and difference between target and actual force is compensated by high bandwidth control of electromagnetic force. A prototype is in the process of production. Demonstration video will be shown on the day of the workshop. REFERENCES [1] I. Sardellitti et al., IROS 2007, pp.1822–1827, 2007. [2] H. Higo, Int. Symp. on Fluid Power 2005, pp.363–368, 2005. [3] T .Noda, Humanoids 2012, pp.21–27, 2012. [4] T. Teramae, T. Noda, J. Morimoto, ICRA2014, pp.4792–4797, 2014. [5] Y. Nakata et al., ICRA 2012, pp.3153–3160, 2012. [6] Y. Nakata et al., IECON 2013, pp.2744–2749, 2013.
Transcript of Design of an Integrated Pneumatic-Electromagnetic Hybrid Linear...
Design of an Integrated Pneumatic-ElectromagneticHybrid Linear Actuator
Yoshihiro Nakata1, Tomoyuki Noda2, Jun Morimoto2 and Hiroshi Ishiguro1
Abstract— We propose a compact direct-drive hybrid actu-ator with pneumatic-electromagnetic integrated structure. Inthis hybrid actuator, pneumatic and electromagnetic actuatorcomponents are perfectly integrated into a compact body. Theactuator can realize both high bandwidth frequency control andhigh power weight ratio. Concept and design of this actuatorare described.
I. INTRODUCTION
Development of mechanisms for humanoid and exoskele-ton robots to realize safe human-robot interaction is an im-portant issue of robotics. High bandwidth variable impedanceand high power/weight ratio actuator is crucial for such kindof applications. However, every actuator with single actuationprinciple has some drawbacks and advantages, and hybridactuators are getting a lot more attention lately [1], [2].
Noda et al. proposed a pneumatic-electric (P-E) hybrid ac-tuator [3] considering an optimal torque distribution methodfor their exoskeleton robot named “XoR” [4]. Output force ofthe actuator is generated by an antagonistic pair of pneumaticartificial muscles and a DC servomotor. However, previoushybrid actuators were made just connecting two types ofactuators via mechanical parts e.g. link, timing belt and gear.Because of this, they tend to become large and fragile dueto their complicated structures.
To solve this problem, we proposed an integratedpneumatic-electromagnetic hybrid linear actuator (IPEHLA).This actuator has an efficiently shared architecture in termsof volume space and force transmission. The pneumatic andthe electromagnetic actuator components share the stator(cylinder) and the mover (piston), and there is no connectionmechanism between them. Force of this actuator can be 10times as large as one of single electromagnetic linear actuatorwith same volume.
II. PROPOSEDHYBRID L INEAR ACTUATOR
The cross-sectional view of proposed hybrid linear ac-tuator is shown in Fig. 1 (iii). Pneumatic and electromag-netic actuators are perfectly integrated into a compact body.The stator and the mover of the electromagnetic actuatorcomponent work as cylinder and piston of the pneumaticactuator component, respectively, and potentially provide thecapability to exploit both advantages of these components.
*This work was supported by MEXT/JSPS KAKENHI (#26540134,#24700203 and #26700026).
1Department of Systems Innovation, Graduate School ofEngineering Science, Osaka University, Osaka, Japan{nakata,ishiguro }@is.sys.es.osaka-u.ac.jp
2Department of Brain Robot Interface, ATR Computational NeuroscienceLaboratories, Kyoto, Japan{t noda, xmorimo }@atr.jp
Servo-valve
Coil
Permanent magnet
Air chamber
Air chamber
Magnetic core
Air sealing plate
Backyoke
Servo-valve
Driving direction Magnetization direction
Foot
Knee
Hip
(i) Robots with EMLAs (ii) Linear vernier motor
(iii) Integrated pneumatic-electromagnetic hybrid linear actuator
Air chamberAir chamber
Fig. 1. Robotic arm with EMLAs, LVM and CAD model of IPEHLA
Thus, no connection mechanism between two actuatorsis necessary. Nakata et al. have been studying a direct-drive electromagnetic linear actuator (EMLA) which cancontrol the output force by quick changes of exiting coilcurrent and enables robots’ joint to have active visco-elasticcharacteristics [5] (See Fig. 1 (i)). Furthermore, a linearvernier motor (LVM) with high force density employingmagnetic gearing effect has been proposed [6] (See Fig. 1(ii)). These electromagnetic structure can be applied to thehybrid actuator and improve the output force and responsecharacteristics. The stator is composed of a back yoke, setsof 3-phase coils and 2 air vents at each end connecting toservo-valves. The back yoke works as magnetic shieldingand a leakage of magnetic flux to outside the actuatoris negligibly small. The mover is composed of sets ofring-shaped permanent magnets (NdFeB) between magneticcores and an air sealing plate at one end. Axially oppositemagnetized magnets are alternatively arranged. Thanks tothis structure, high magnetic flux can be generated, especiallythe effective radial component of flux with an inward andoutward direction from the magnetic cores. Output force isbroadly controlled by compressed air and difference betweentarget and actual force is compensated by high bandwidthcontrol of electromagnetic force. A prototype is in theprocess of production. Demonstration video will be shownon the day of the workshop.
REFERENCES
[1] I. Sardellitti et al.,IROS 2007, pp.1822–1827, 2007.[2] H. Higo, Int. Symp. on Fluid Power 2005, pp.363–368, 2005.[3] T .Noda,Humanoids 2012, pp.21–27, 2012.[4] T. Teramae, T. Noda, J. Morimoto,ICRA2014, pp.4792–4797, 2014.[5] Y. Nakata et al.,ICRA 2012, pp.3153–3160, 2012.[6] Y. Nakata et al.,IECON 2013, pp.2744–2749, 2013.
