SLIP-Based Control of Bipedal Walking Based on Two-Level Control Strategy

In this research, we propose a two-level control strategy for simultaneous gait generation and stable control of planar walking of the Assume The Robot Is A Sphere (ATRIAS) biped robot with unlocked torso, utilizing active spring-loaded inverted pendulum (ASLIP) as reference models. The upper level consists of an energy-regulating control calculated using the ASLIP model, producing reference ground reaction forces (GRFs) for the desired gait. In the lower level controller, PID force controllers for the motors ensure tracking of the reference GRFs for ATRIAS direct dynamics. Meanwhile, ATRIAS torso angle is controlled stably to make it able to follow a point mass template model. Advantages of the proposed control strategy include simplicity and efficiency. Simulation results using ATRIAS’s complete dynamic model show that the proposed two-level controller can reject initial condition disturbances while generating stable and steady walking motion

Modeling and Optimized Gait Planning of Biped Robots with Different Leg Mechanisms

This research focuses on modeling and gait generation optimization of four different real biped models that include practical extended models of the theoretical SLIP and compass gait as a novelty of the work. The first model is kneed Biped model without spring that is a 5-rigid-link robot with four actuators in its hip and knees. The second model, kneed biped model with springs in shins is very similar to the first model, but its shins have linear springs. The 3rd model is a semi-telescopic springy biped model and the 4th model is a semi-compass gait with kneed swing leg. Optimization parameters of their walking gait, objective functions and constraints are presented and successive stages of optimization are completed to find the optimal gaits. The efficiency of the gaits and required motor torques for the optimal gait of each model are illustrated

Non-contact AC current measurement using vibration analysis of a MEMS piezoelectric cantilever beam

This paper proposes a non-contact system to measure electrical current crossing a wire. To do so, design and simulation of a piezoelectric cantilever beam with a tip mass is presented using mathematical modeling. The sandwich cantilever beam is composed of two piezoelectric layers and a mid-layer made up of steel. For mathematical modeling, the governing differential equation of the beam is extracted and solved by Galerkin method. Then the output voltage is calculated for different values of external forces. The force applied to the tip mass from the magnetic field of wire is used as external excitation force of the beam. According to the response of the output voltage, the current crossing the wire is calculated. Validation of the model is demonstrated compared to other references. In results section, frequency response behavior and influence of the geometric parameters on output voltage are analyzed. Appropriate values of these parameters should be used in design process of this non-contact sensor to have an observable applied force from the current carrying wire

Design, modeling and control of a soft gripper with TCP actuator using image processing

Artificial muscles have gained importance due to their high deformability, which is used in soft robots. In this article, to further exploit and understand the behavior of TCP muscles, as well as to control these muscles more easily, we mathematically model the stimulus, which includes a model to understand the temperature behavior of muscles with changes in flow and amount of displacement due to changes in temperature and amount of external force. is. By designing a soft gripper and applying the necessary restrictions, we get the force needed to move this gripper. Then we obtain the inematic model of the finger to obtain the bending angle due to the displacement of the muscle which is connected to the fingers and gripper by the cable. We also check the muscle's ability to perform this movement. In the next step, programming and implementation of a simple model of turning on and off the heating and cooling system to create expansion and contraction in the muscle is done by image processing on the Arduino controller to control the system. Using the obtained models and taking into account different and important values in the models, we extracted the related diagrams and checked and compared them. From these results, we can point out the changes in the temperature behavior and movement of the muscle with the change in the input current as well as the type of alloy used, the controllability of the muscle, and the ability of the muscle to move the gripper

Compliant Leg Architectures and a Linear Control Strategy for the Stable Running of Planar Biped Robots

This paper investigates two fundamental structures for biped robots and a control strategy to achieve stable biped running. The first biped structure contains straight legs with telescopic springs, and the second one contains knees with compliant elements in parallel with the motors. With both configurations we can use a standard linear discrete-time state-feedback control strategy to achieve an active periodic stable biped running gait, using the Poincare map of one complete step to produce the discrete-time model. In this case, the Poincare map describes an open-loop system with an unstable equilibrium, requiring a closed loop control for tabilization. The discretization contains a stance phase, a flight phase and a touch-down. In the first approach, the control signals remain constant during each phase, while in the second approach both phases are discretized into a number of constant-torque intervals, so that its formulation can be applied easily to stabilize any active biped running gait. Simulation results with both the straight-legged and the kneed biped model demonstrate stable gaits on both horizontal and inclined surfaces

Investigation of Nonlinear Thermo-Elastic Behavior of Fluid Conveying Piezoelectric Microtube Reinforced by Functionally Distributed Carbon Nanotubes on Viscoelastic-Hetenyi Foundation

In this paper, nonlinear and nonlocal thermo-elastic behavior of a microtube reinforced by Functionally Distributed Carbon Nanotubes, with internal and external piezoelectric layers, in the presence of nonlinear viscoelastic-Hetenyi foundation, and axial fluid flow inside the microtube is studied. Nonlinear partial differential equations governing the system are derived using Reddy’s third-order shear deformations theory along with the Von-Karman theory including the effect of fluid viscosity. Then, the equations are converted to time-dependent ordinary nonlinear equations using the Galerkin method. Afterward, the governing equations of the microtube’s lateral displacements are solved using the multiple scales method. The analysis of the piezoelectric’s parametric resonance is performed by obtaining trivial and nontrivial stationary solutions and plotting characteristic curves of the frequency response and voltage response. At the end, the effect of different parameters including the flow velocity, excitation voltage, parameters of the foundation, viscosity parameter, thermal loading and nanotubes’ volume fraction index on the nonlinear behavior of the system, under parametric resonance condition, is investigated