scholarly journals Dynamical Modeling and Control of Modular Snake Robots With Series Elastic Actuators for Pedal Wave Locomotion on Uneven Terrain

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Mohammadali Javaheri Koopaee ◽  
Christopher Pretty ◽  
Koen Classens ◽  
XiaoQi Chen
Keyword(s):  
Wave Motion ◽  
Vertical Plane ◽  
Contact Forces ◽  
Contact Model ◽  
Lagrange Equations ◽  
Uneven Terrain ◽  
Contact Points ◽  
Series Elastic Actuators ◽  
Snake Robots ◽  
Series Elastic

Abstract This paper introduces the equations of motion of modular 2D snake robots moving in vertical plane employing Series Elastic Actuators (SEAs). The kinematics of such 2D modular snake robot is presented in an efficient matrix form and Euler–Lagrange equations are constructed to model the robot. Moreover, using a spring-damper contact model, external contact forces, necessary for modeling pedal wave motion (undulation in the vertical plane) are taken into account, which unlike existing methods can be used to model the effect of multiple contact points. Using such a contact model, pedal wave motion of the robot is simulated and the torque signal measured by the elastic element from the simulation and experimentation are used to show the validity of the model. Moreover, pedal wave locomotion of such robot on uneven terrain is also modeled and an adaptive controller based on torque feedback in gait parameter's space with optimized control gain is proposed. The simulation and experimentation results showed the efficacy of the proposed controller as the robot successfully climbed over a stair-type obstacle without any prior knowledge about its location with at least 24.8% higher speed compared with non-adaptive motion.

scholarly journals Dynamical Modelling and Control of Snake-Like Motion in Vertical Plane for Locomotion in Unstructured Environments

2019 ◽  
Author(s):  
Mohammadali Javaheri Koopaee ◽  
Christopher Pretty ◽  
Koen Classens ◽  
XiaoQi Chen
Keyword(s):  
Wave Motion ◽  
Force Feedback ◽  
Equations Of Motion ◽  
Vertical Plane ◽  
Adaptive Controller ◽  
Contact Forces ◽  
Lagrange Method ◽  
Uneven Terrain ◽  
And Control ◽  
Snake Robots

Abstract This paper introduces the equations of motion of modular 2D snake robots in the vertical plane. In particular, the kinematics of pedal wave motion (undulation in vertical plane) of modular snake robots is presented and using the Euler-Lagrange method, the equations of motion of the robot are obtained. Moreover, using the well-known Spring-Damper contact model, external contact forces are taken into account and pedal wave locomotion on uneven terrain is modelled and simulated. Enabled by the dynamical model of the robot, an adaptive controller based on external force feedback in gait parameter space is proposed and implemented, resulting in the robot to successfully climbing over a stair-type obstacle without any prior knowledge about the environment.

Hopping frequency influences elastic energy reuse with joint series elastic actuators

2021 ◽  
Vol 119 ◽  
pp. 110319
Author(s):  
A. Mohammadi Nejad Rashty ◽  
M. Grimmer ◽  
A. Seyfarth
Keyword(s):  
Elastic Energy ◽  
Series Elastic Actuators ◽  
Series Elastic

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

scholarly journals Design and Calibration of Robot Base Force/Torque Sensors and Their Application to Non-Collocated Admittance Control for Automated Tool Changing

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 2895
Author(s):  
Hubert Gattringer ◽  
Andreas Müller ◽  
Philip Hoermandinger
Keyword(s):  
Steel Plate ◽  
Robotic Manipulators ◽  
Indirect Measurement ◽  
Local Deformation ◽  
Contact Forces ◽  
The Novel ◽  
Admittance Control ◽  
Load Cells ◽  
Series Elastic Actuators ◽  
Automated Tool

Robotic manipulators physically interacting with their environment must be able to measure contact forces/torques. The standard approach to this end is attaching force/torque sensors directly at the end-effector (EE). This provides accurate measurements, but at a significant cost. Indirect measurement of the EE-loads by means of torque sensors at the actuated joint of a robot is an alternative, in particular for series-elastic actuators, but requires dedicated robot designs and significantly increases costs. In this paper, two alternative sensor concept for indirect measurement of EE-loads are presented. Both sensors are located at the robot base. The first sensor design involves three load cells on which the robot is mounted. The second concept consists of a steel plate with four spokes, at which it is suspended. At each spoke, strain gauges are attached to measure the local deformation, which is related to the load at the sensor plate (resembling the main principle of a force/torque sensor). Inferring the EE-load from the so determined base wrench necessitates a dynamic model of the robot, which accounts for the static as well as dynamic loads. A prototype implementation of both concepts is reported. Special attention is given to the model-based calibration, which is crucial for these indirect measurement concepts. Experimental results are shown when the novel sensors are employed for a tool changing task, which to some extend resembles the well-known peg-in-the-hole problem.

A convex optimization framework for robust-feasible series elastic actuators

Mechatronics ◽  
2021 ◽  
Vol 79 ◽  
pp. 102635
Author(s):  
Edgar A. Bolívar-Nieto ◽  
Tyler Summers ◽  
Robert D. Gregg ◽  
Siavash Rezazadeh
Keyword(s):  
Convex Optimization ◽  
Optimization Framework ◽  
Series Elastic Actuators ◽  
Series Elastic

Periodic Response of a Link Coupling With Clearance

1989 ◽  
Vol 111 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Y. S. Choi ◽  
S. T. Noah
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Solution Procedure ◽  
Contact Forces ◽  
Steady State Response ◽  
Algebraic Equations ◽  
State Response ◽  
Contact Points ◽  
Integration Schemes ◽  
Nonlinear Algebraic Equations

The nonlinear, steady-state response of a displacement-forced link coupling with clearance with finite stiffness is determined. The solution procedure is derived from satisfying the boundary conditions at the contact points and then solving the resulting nonlinear algebraic equations by setting the duration of contact as a parameter. This direct approach to determining periodic solutions for systems with clearances with finite stiffness is substantially more efficient than numerical integration schemes. Results in terms of contact forces and durations of contact are pertinent to fatigue and wear studies. Parametric relations are presented for effects of the variation of damping, stiffness, exciting displacement, and gap length on the dynamic behavior of the link pair.

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