Using parallel stiffness to achieve improved locomotive efficiency with the Sandia STEPPR robot

Mazumdar, Anirban; Spencer, Steve J.; Salton, Jonathan R.; Hobart, Clinton G.; Love, Joshua; Dullea, Kevin J.; Kuehl, Michael; Blada, Timothy; Quigley, Morgan; Smith, Jesper; Bertrand, Sylvain; Wu, Tingfan; Pratt, Jerry; Buerger, Stephen

doi:10.1109/icra.2015.7139275

Cited by 10 publications

(8 citation statements)

References 14 publications

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“…If the desired motions of the robot are known beforehand, the elastic element can take them into account, thereby providing some of the force required for that motion. This approach has already led to large reductions in energy consumption for different repetitive tasks [3], [5], [8]- [10]. These designs all aim to capture kinetic energy from the robot arm, and release that energy again at appropriate times in the motion.…”

Section: Introductionmentioning

confidence: 99%

“…Due to the limited amount of energy available, finding the exact optimal spring characteristic is vital. The optimization approaches for task specific spring mechanisms in literature can be classified into the following three categories: 1) A linear spring is fit to trajectory data [8], [10]. Peak power is reduced, but the fit becomes poorer as the desired characteristic gets more nonlinear.…”

Section: Introductionmentioning

confidence: 99%

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Unparameterized Optimization of the Spring Characteristic of Parallel Elastic Actuators

Spaa

Wolfslag

Wisse

2019

IEEE Robot. Autom. Lett.

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In electrically actuated robots most energy losses are due to the heating of the actuators. This energy loss can be greatly reduced with parallel elastic actuators, by optimizing the elastic element such that it delivers most of the required torques. Previously used optimization methods relied on parameterizing the spring characteristic, thereby limiting the set of spring characteristics optimized over and with that the loss reduction that can be obtained. This paper shows that such parametrization is not necessary; a method is presented to compute the optimal characteristic as an analytic function of the trajectory. The efficacy of this method is demonstrated using two examples. The first example considers the optimal spring characteristic for a parallel elastic actuator supporting the human ankle during walking. The second example applies the method in combination with trajectory optimization on a single degree of freedom robot performing a specific pick-andplace task. The task at hand has a height difference between the pick and the place location. With the analytical optimal spring, it is shown that the robot can recover enough of the energy released by the package to function without external electric energy supply.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Unparameterized Optimization of the Spring Characteristic of Parallel Elastic Actuators

Spaa

Wolfslag

Wisse

2019

IEEE Robot. Autom. Lett.

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“…The parallel elasticity (PE) was initially used to statically counterbalance the articulated robot for upper arms [17]. The applications of PEAs in recent years have been focused on walking robotics in multiple degrees of the human lower limb, such as hip flexion-extension [16], [18], hip adductionabduction [19], knee flexion-extension [13], [20]- [25] and ankle dorsi-plantar flexion [19], [26]- [28]. The simulation results during a normal walking gait showed that a unidirectional PE at the hip joint in the sagittal plane could reduce average (root mean square, rms) and peak motor power by 50 and 13.9 %, respectively [29].…”

mentioning

confidence: 99%

“…The leaf spring is also commonly used as the PE due to its high stiffness, such as the parallel SEA-driven knee joint of the running robot Phides [13] and the series PEA-driven hip joint of the LLE [16]. Moreover, a few researchers adopted the spiral spring (see the STEPPR robot [19]), the compression coil spring [18], [27], [28], the magnetic non-linear torsion spring [5], the Belleville spring [26] and the bungee cord (see the hip joint for a back-support exoskeleton [40], [41]). There are two common characteristics summarized among these PEA designs.…”

mentioning

confidence: 99%

“…Following the predetermined reduction ratio of the PEA and gait of the hip joint from [29], the key point is to evaluate the effect of the PE on increasing the power efficiency of the motor. Various evaluation indexes are used, including electrical work [19], [32], [33], [37], [42]- [44], positive electrical work [7], [11], absolute electrical work [45], [46], positive mechanical work [7], [11], resistive loss [7], [11], absolute mechanical work [25], [26], average (rms) mechanical power [4], peak electrical power [28], [43]- [46], peak torque [32], [33] and rms torque [4], [36] of the motor. The reversing power flow from the load is not regenerated by our motor.…”

mentioning

confidence: 99%

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Analysis, Design, and Preliminary Evaluation of a Parallel Elastic Actuator for Power-Efficient Walking Assistance

Guan

et al. 2020

IEEE Access

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This paper introduces the analysis, design and preliminary evaluation of a self-integrated parallel elastic actuator (PEA) with an electric motor and a flat spiral spring in parallel to drive the hip joint of lower limb exoskeletons for power-efficient walking assistance. Firstly, we quantitatively analyze the reason why the parallel elasticity (PE) placed at the sagittal hip joint can reduce the motor power requirement during walking assistance, which contributes to the theory of PEA development and application. The design of the PEA is then introduced in detail. The novelty of the design is that the actuator is reduced in size by integrating the spring into the motor, and the requirement of spring stiffness is significantly reduced by placing the spring directly parallel to the motor shaft. Furthermore, both the simulation based on dynamic modeling and benchtop experiment are conducted preliminarily to evaluate the performance of the PEA with nine spring stiffnesses in a range from 0-5.29 mN•m/rad regarding two indexes including the average and maximum positive electrical power of the motor. Their results show that the two indexes become smaller when the PE is attached and decrease as the spring stiffness increases. When the PE with a stiffness of 5.29 mN•m/rad is attached, the actuator obtains the largest reduction rate of 11.99 and 16.84 % in the average (root mean square) and maximum positive electrical power of the motor in the simulation and 10.3 and 26.25 % in the experiment, respectively. Those results provide evidence for the applicability of the newly designed PEA in driving a lower limb exoskeleton with high power efficiency during walking assistance for paraplegic patients with complete loss in walking ability. INDEX TERMS Actuator design, compliant actuation, lower limb exoskeleton, parallel elastic actuator, power-efficient actuator. I. INTRODUCTION Traditional rigid actuators (RAs) (e.g. electric motors), as the key units of walking assistance devices such as lower limb exoskeletons (LLEs), consume a lot of power, leading to a high power requirement. An average power of nearly 600 W, for example, was required during level-ground walking at 1.3 m/s with the exoskeleton BLEEX actuated by motors [1]. Therefore, it is important to develop power-efficient actuators for walking assistance. The associate editor coordinating the review of this manuscript and approving it for publication was Yangmin Li .

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Series Parallel Elastic Actuator: Variable Recruitment of Parallel Springs for Partial Gravity Compensation

Furnémont

Mathijssen

Verstraten

et al. 2022

Gravity Compensation in Robotics

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Using parallel stiffness to achieve improved locomotive efficiency with the Sandia STEPPR robot

Cited by 10 publications

References 14 publications

Unparameterized Optimization of the Spring Characteristic of Parallel Elastic Actuators

Unparameterized Optimization of the Spring Characteristic of Parallel Elastic Actuators

Analysis, Design, and Preliminary Evaluation of a Parallel Elastic Actuator for Power-Efficient Walking Assistance

Series Parallel Elastic Actuator: Variable Recruitment of Parallel Springs for Partial Gravity Compensation

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