This paper provides a detailed analysis of the power and mechanical/electrical energy consumption of Series Elastic Actuators (SEAs) and Parallel Elastic Actuators (PEAs). The study is done by imposing a sinusoidal motion to a pendulum load, such that the natural dynamics automatically present itself in the power and energy consumption. This allows to link the actuators' dynamics to their loss mechanisms, revealing interesting characteristics of series and parallel elastic elements in actuator designs. Simulations demonstrate that the SEA and PEA allow to decrease both peak power and energy consumption, provided that the stiness of their elastic element is tuned properly. For the SEA, both are minimized by tuning the elastic element to the antiresonance frequency of the actuator. For the PEA, peak power is minimal at the link's resonance frequency, but the optimal stiness for minimal electrical energy consumption cannot be determined by a theoretical resonance and needs to be calculated using a complete system model. If these guidelines are followed, both types of elastic actuators can provide signicant energetic benets at high frequencies. This was conrmed by experiments, which demonstrated energy reductions of up to 78% (SEA) and 20% (PEA) compared to rigid actuators.
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%.
Locking devices are widely used in robotics, for instance to lock springs, joints or to reconfigure robots. This review paper classifies the locking devices currently described in literature and preforms a comparative study. Designers can, as such, better determine which locking device best matches the needs of their application. The locking devices are divided into three main categories based on different locking principles: mechanical locking, friction-based locking and singularity locking. Different lockers in each category can be passive lockers or active lockers. Based on an elaborate literature study, the paper summarizes the findings by comparing different locking devices, based on a set of properties of a theoretical ideal locking device.
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