Mechanical damping with electrical regeneration for a powered transfemoral prosthesis

a b s t r a c tEnergy efficiency is a growing concern in today's mechatronic designs. In recent years, many works have emerged presenting energy-efficient actuators with electrical motors. However, there is little consistency in the way energy consumption is calculated. Drive inertia, motor efficiency and controller efficiency are often neglected in optimizations, and so are the load-and speed-dependency of the losses and other non-linearities. While this approach works well in stationary circumstances, it can lead to significant errors in highly dynamic tasks with a wide range of operation, such as the ones faced by actuators in the field of robotics. This paper discusses the losses occurring in an actuator consisting of a DC motor and gearbox as it is forcing a swinging motion on a pendulum. From this simple case study, some general recommendations on the modeling of energy losses are formulated. Combining data from manufacturer's datasheets with empirical data, the approach presented in this paper was able to predict the energy consumption for this specific case with an error of less than 10%.

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“…h ¼0 or T m ¼ 0) [26]. This is evidenced by a map showing steady-state motor efficiency as a function of speed and torque ( Fig.…”

Section: Motor Efficiencymentioning

confidence: 96%

“…The mechanical energy curve represents E mech as defined in Eq. (26); it comprises all energy losses except electrical losses. As the amount of energy which can be regenerated increases, the frequency of minimum energy consumption shifts from the entire system's natural frequency, xs, to the natural frequency of the pendulum alone, xp.…”

Section: Set-upmentioning

confidence: 99%

Modeling and design of geared DC motors for energy efficiency: Comparison between theory and experiments

et al. 2015

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“…regenerative powertrains have focused exclusively on level-ground walking [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][33][34][35]. However, geriatric and rehabilitation patients often exhibit slower walking speeds (e.g., 24 % speed reduction from 25 to 75 years age) and take fewer steps/day (e.g., 75 % reduction from 60 to 85 years age) [3], therein limiting the potential for energy regeneration during level-ground walking.…”

Section: Previous Investigations Of Lower-limb Prostheses and Exoskelmentioning

confidence: 99%

“…Analogous to electric and hybrid electric vehicles [13][14], several biomechatronic knee designs have incorporated regenerative powertrains to convert the otherwise dissipated joint biomechanical energy during legged locomotion into electrical energy for recharging the onboard batteries while providing negative mechanical work for controlled system deceleration [5,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. These energy-efficient powertrains can enable lighter onboard batteries and/or extend the operating durations between recharging.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Stand-to-Sit Biomechanics for Design of Lower-Limb Exoskeletons and Prostheses with Energy Regeneration

Laschowski¹,

Razavian²,

McPhee³

2019

Preprint

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BACKGROUND: Regenerative powertrain systems can extend the operating durations of robotic lower-limb prostheses and exoskeletons. These energy-efficient biomechatronic devices have been exclusively designed and evaluated for level-ground walking. Building on previous investigations, this research assessed the lower-limb joint biomechanical powers during stand-tosit movements using inverse dynamics modelling to estimate the biomechanical energy available for electrical regeneration. METHODS: Nine participants performed 20 sitting and standing movements while lower-limb kinematics and ground reaction forces were measured. Following the biomechanical model design, dynamic parameter identification computed the subject-specific body segment inertial parameters that minimized the differences in ground reaction forces and moments between the experimental measurements and inverse dynamic simulations. Joint biomechanical powers were calculated from net joint torques and rotational velocities and numerically integrated over time to determine biomechanical energy. RESULTS: The hip joint generated the largest maximum negative biomechanical power (1.8 ± 0.5 W/kg), followed by the knee joint (0.8 ± 0.3 W/kg) and ankle joint (0.2 ± 0.1 W/kg). Negative biomechanical energy from the hip, knee, and ankle joints per stand-to-sit movement were 0.36 ± 0.06 J/kg, 0.16 ± 0.08 J/kg, and 0.03 ± 0.01 J/kg, respectively. CONCLUSIONS: Using previously published maximum energy regeneration efficiencies (i.e., approximately 37 %), robotic knee prostheses and exoskeletons could theoretically regenerate 0.06 ± 0.03 J/kg of electrical energy while sitting down. These findings have implications on design optimization of regenerative powertrains for energy-efficient lower-limb biomechatronic devices.

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“…Although much implementation and analysis of MPC is conducted This is closely related to the concept of energy harvesting to supply some or all of the semi-active control system power requirements (Nakano et al 2003, Scruggs et al 2007a. The concept of "energy harvesting" is closely related to that of "regeneration" (Seth andFlowers 1990, Tucker andFite 2010).…”

Section: Introductionmentioning

confidence: 99%

Power-constrained intermittent control

Gawthrop

Wagg

Neild

et al. 2013

International Journal of Control

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In this paper input power, as opposed to the usual input amplitude, constraints are introduced in the context of intermittent control. They are shown to result in a combination of quadratic optimisation and quadratic constraints. The main motivation for considering input power constraints is its similarity with semi-active control. Such methods are commonly used to provide damping in mechanical systems and structures. It is shown that semi-active control can be re-expressed and generalised as control with power constraints and can thus be implemented as power-constrained intermittent control. The method is illustrated using simulations of resonant mechanical systems and the constrained nature of the power flow is represented using power-phaseplane plots. We believe the approach we present will be useful for control design of both semi-active and low-power vibration suppression systems.

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Mechanical damping with electrical regeneration for a powered transfemoral prosthesis

Cited by 27 publications

References 14 publications

Modeling and design of geared DC motors for energy efficiency: Comparison between theory and experiments

Modeling and design of geared DC motors for energy efficiency: Comparison between theory and experiments

Simulation of Stand-to-Sit Biomechanics for Design of Lower-Limb Exoskeletons and Prostheses with Energy Regeneration

Power-constrained intermittent control

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