Linear multi-modal actuation through discrete coupling

Leach, Derek; Günther, Fabian; Maheshwari, Nandan; Iida, Fumiya

doi:10.1109/iros.2012.6385867

Cited by 6 publications

(3 citation statements)

References 17 publications

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“…Novel design concepts, such as those using a variable stiffness spring [7] or antagonist non-linear devices [8], can alter the stiffness continually, yet the variable range is rather limited. A promising approach using a series-compliance that can be locked with a brake vary the impedance in a broader range [9]. Another concept is a dual actuator systems using EM motors in a serial configuration, one controlling the position and the other the impedance [10].…”

Section: Related Workmentioning

confidence: 99%

A two-speed actuator for robotics with fast seamless gear shifting

Girard

Asada

2015

2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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This paper present a novel dual-speed actuator adapted to robotics. In many applications, robots have to bear large loads while moving slowly and also have to move quickly through the air with almost no load. This lead to conflicting requirements for their actuators. Multiple gear ratios address this issue by allowing an effective use of power over a wide range of torque-speed load conditions. Furthermore, very different gear ratios also lead to drastic changes of the intrinsic impedance, enabling a non-back-drivable mode for stiff position control and a back-drivable mode for force control. The proposed actuator consists of two electric motors coupled to a differential; one has a large gear ratio while the other is almost direct-drive and equipped with a brake. During the high-force mode the brake is locked, only one motor is used, and the actuator behaves like a regular highly-geared servo-motor. During the high-speed mode the brake is open, both motor are used at the same time, and the actuator behaves like a direct drive motor. A dynamic model is developed and novel controllers are proposed for synergic use of both motors. The redundancy of motors is exploited for maintaining full control of the output during mode transitions, allowing for fast and seamless switching even when interacting with unknown environments. Results are demonstrated with a proof-of-concept linear actuator.

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Section: Related Workmentioning

confidence: 99%

A two-speed actuator for robotics with fast seamless gear shifting

Girard

Asada

2015

2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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“… 7. In recent years, researchers have experimented with clutches and brakes added to SEA to control the release of the stored energy (e.g. Leach et al, 2012; Laffranchi et al, 2014). However, these prototype actuators have not yet been tested on highly dynamic and versatile legged robots. …”

mentioning

confidence: 99%

Towards versatile legged robots through active impedance control

Semini

Barasuol

Boaventura

et al. 2015

The International Journal of Robotics Research

154

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Robots with legs and arms have the potential to support humans in dangerous, dull or dirty tasks. A major motivation behind research on such robots is their potential versatility. However, these robots come at a high price in mechanical and control complexity. Hence, until they can demonstrate a clear advantage over their simpler counterparts, robots with arms and legs will not fulfill their true potential. In this paper, we discuss the opportunities for versatile robots that arise by actively controlling the mechanical impedance of joints and particularly legs. In contrast to passive elements such as springs, active impedance is achieved by torque-controlled joints allowing real-time adjustment of stiffness and damping. Adjustable stiffness and damping in real-time is a fundamental building block towards versatility. Experiments with our 80 kg hydraulic quadruped robot HyQ demonstrate that active impedance alone (i.e. no springs in the structure) can successfully emulate passively compliant elements during highly dynamic locomotion tasks (running, jumping and hopping); and that no springs are needed to protect the actuation system. Here we present results of a flying trot, also referred to as a running trot. To the best of the authors' knowledge this is the first time a flying trot has been successfully implemented on a robot without passive elements such as springs. A critical discussion on the pros and cons of active impedance concludes the paper. This article is an extension of our previous work presented at the International Symposium on Robotics Research (ISRR) 2013.

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“…Discrete mode of operations are present in many system, such as powertrains with multiple gear ratios, pneumatic or hydraulic systems equipped with on/off valves and special actuators [4] [3] [5]. Considering the global behavior of such systems, including the mode selection, lead to a hybrid dynamical model.…”

Section: A Related Workmentioning

confidence: 99%

A practical optimal control approach for two-speed actuators

Girard

Asada

2016

2016 IEEE International Conference on Robotics and Automation (ICRA)

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This paper addresses the closed-loop control of an actuator with both a continuous input variable (motor torque) and a discrete input variable (mode selection). In many applications, robots have to bear large loads while moving slowly and also have to move quickly through the air with almost no load, leading to conflicting requirements for their actuators. An actuator with multiple gear ratios, like in a powertrain, can address this issue by allowing an effective use of power over a wide range of output speed. However, having discrete modes of operation adds complexity to the high-level control and planning. Here a controller for two-speed actuators that automatically select both the best gear ratio and the motor torque is developed. The approach is to: first derive a low-dimensional model, then use dynamic programming to find the best actions for all possible situations, and last use regression analysis to extract simplified global feedback laws. This approach produces simple practical nearly-optimal feedback laws. A controller that globally minimizes a quadratic cost function is derived for a two-speed actuator prototype, global stability is proven and performance is demonstrated experimentally.

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Linear multi-modal actuation through discrete coupling

Cited by 6 publications

References 17 publications

A two-speed actuator for robotics with fast seamless gear shifting

A two-speed actuator for robotics with fast seamless gear shifting

Towards versatile legged robots through active impedance control

A practical optimal control approach for two-speed actuators

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