This article expounds the design and control of a new variable stiffness series elastic actuator (VSSEA). It is established by employing a modular mechanical design approach that allows us to effectively optimize the stiffness modulation characteristics and power density of the actuator. The proposed VSSEA possesses the following features: no limitation in the work range of output link; a wide range of stiffness modulation (∼20 N·m/rad to ∼1 KN·m/rad); low-energy-cost stiffness modulation at equilibrium and nonequilibrium positions; compact design and high torque density (∼36 N·m/kg); and high-speed stiffness modulation (∼3000 N·m/rad/s). Such features can help boost the safety and performance of many advanced robotic systems, e.g., a cobot that physically interacts with unstructured environments and an exoskeleton that provides physical assistance to human users. These features can also enable us to utilize variable stiffness property to attain various regulation and traje
Actuators
Ompliant-robotics
Mechatronics
Emodulation
Hysical-robot-environment-interaction
Robots
Afe-robotics
Eries-elastic-actuators-seas-
Solid-modeling
Springs
Porque
Wire and arc additive manufacturing(WAAM) is a promising method for directly manufacturing parts with complex shapes. However, the accuracy of the existing welding parameter planning methods would dramatically decrease when bead geometry changes dynamically due to the long-term dependence, strong coupling, and hysteresis properties of the WAAM process. To this end, a non-autoregressive(NAR) dynamic model is proposed to predict the bead geometry, and an adaptive model predictive control(aMPC) method is proposed to plan welding parameters to achieve high manufacturing accuracy. First, in the proposed dynamic model, the long-term dynamic characteristics of the WAAM process are modeled by a resample long short-term memory(Re-LSTM) network by considering the fluidity of the welding pool, which is the crucial factor of dynamic characteristics of the welding process. Second, in the proposed aMPC method, the strong coupling is addressed by high multi-objective performance, and the hysteresis i
Adaptation-models
M
Geometry
On-autoregressive-dynamic-model
Planning
Predictive-models
Process-control
Solid-modeling
Arying-geometry-beads
Aam
Welding
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