scholarly journals Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Robotica ◽  
2021 ◽  
pp. 1-22
Author(s):  
Paul Milenkovic
Keyword(s):  
Small Deviation ◽  
Optimal Path ◽  
Kinematic Model ◽  
Path Following ◽  
Maximum Deviation ◽  
Exclusion Zone ◽  
Step Size ◽  
Spherical Wrist ◽  
Serial Robot ◽  
Control Step

Abstract An unexpected path reversal is discovered for a serial robot with an offset-axis wrist over a finite range of proximity to the wrist singularity. This is replicated by a kinematic model. A prior spherical-wrist method transits the singularity with limited joint rate and acceleration under a constant rate of tool traversal. Accurate position is maintained by controlling a small deviation in orientation. Extensions to the method for an offset wrist (1) find the least-maximum deviation, (2) identify and locate where a path reversal occurs, and (3) use this point to control step size in a high-order predictor-correction path following procedure.

Serial-robot Wrist-singularity Mitigation Along Alternative Optimally Adjusted Paths

2021 ◽  
Author(s):  
Paul H. Milenkovic
Keyword(s):  
Kinematic Model ◽  
Path Following ◽  
Close Approach ◽  
Optimal Level ◽  
Singularity Method ◽  
Constant Rate ◽  
Robot Wrist ◽  
Serial Robot ◽  
Tool Position ◽  
Virtual Joints

Abstract Adjusting the displacement path of a serial robot encountering the wrist singularity to pass either through the singularity or around it mitigates its adverse effects. Both such path adjustments are commonly called singularity avoidance and are applied here to either a spherical or an offset wrist. These adjustments avoid high joint rates that can occur at singularity encounter. A recent through-the singularity method limits joint rates and accelerations in the robot with either a spherical or offset wrist when conducting a constant rate of traversal of the tool manipulated by the robot. A kinematic model adding multiple virtual joints allows a modified high-order path-following algorithm to maintain accurate tool position while achieving an optimal level of tool deviation in orientation. Whereas a path reversal resulting from a turning-point type singularity had been revealed for an offset wrist over a finite range of close-approach, these conditions are met when connecting the isolated path segments. Procedures are developed here with this capability for an around-the-singularity path. Choosing between the through and around-singularity alternatives offers the overall optimum.

scholarly journals Optimal Path-Following Guidance with Generalized Weighting Functions Based on Indirect Gauss Pseudospectral Method

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Qi Chen ◽  
Xugang Wang ◽  
Jing Yang
Keyword(s):  
Degrees Of Freedom ◽  
Optimal Path ◽  
Pseudospectral Method ◽  
Path Following ◽  
Control Cost ◽  
Weighting Functions ◽  
Guidance Law ◽  
Computational Performance ◽  
Gauss Pseudospectral Method ◽  
Virtual Target

An indirect Gauss pseudospectral method based path-following guidance law is presented in this paper. A virtual target moving along the desired path with explicitly specified speed is introduced to formulate the guidance problem. By establishing a virtual target-fixed coordinate system, the path-following guidance is transformed into a terminal guidance with impact angle constraints, which is then solved by using indirect Gauss pseudospectral method. Meanwhile, the acceleration dynamics are modeled as the first-order lag to the command. Using the receding horizon technique a closed-loop guidance law, which considers generalized weighting functions (even discontinuous) of both the states and the control cost, is derived. The accuracy and effectiveness of the proposed guidance law are validated by numerical comparisons. A STM32 Nucleo board based on the ARM Cortex-M7 processor is used to evaluate the real-time computational performance of the proposed indirect Gauss pseudospectral method. Simulations for various types of desired paths are presented to show that the proposed guidance law has better performance when compared with the existing results for pure pursuit, a nonlinear guidance law, and trajectory shaping path-following guidance and provides more degrees of freedom in path-following guidance design applications.

Adaptive Optimal Path Following for High Wind Flights

2011 ◽  
Vol 44 (1) ◽  
pp. 12985-12990 ◽  
Author(s):  
Ashwini Ratnoo ◽  
P.B. Sujit ◽  
Mangal Kothari
Keyword(s):  
Optimal Path ◽  
Path Following ◽  
High Wind

scholarly journals A Simplified Optimal Path Following Controller for an Agricultural Skid-Steering Robot

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 95932-95940 ◽  
Author(s):  
Benjamin Fernandez ◽  
Pedro Javier Herrera ◽  
Jose Antonio Cerrada
Keyword(s):  
Optimal Path ◽  
Path Following ◽  
Skid Steering

Hovering Control of Outdoor Blimp Robots Based on Path Following

2011 ◽  
Vol 23 (2) ◽  
pp. 207-214 ◽  
Author(s):  
Hitomu Saiki ◽  
◽  
Takanori Fukao ◽  
Takateru Urakubo ◽  
Takashi Kohno ◽  
...  
Keyword(s):  
Pid Control ◽  
Large Scale ◽  
Design Method ◽  
Optimal Path ◽  
Path Following ◽  
Proportional Integral Derivative ◽  
Longitudinal Plane ◽  
Path Following Control ◽  
Strong Winds ◽  
Hovering Control

After large-scale disasters, a surveillance system is required to gather information about the stricken area safely and quickly. An autonomous blimp is the best option for this purpose. This paper proposes a control design method for automatic hovering of outdoor blimp robots under strong winds by a path-following approach. The method consists of inverse optimal path-following control in the horizontal plane and Proportional-Integral-Derivative (PID) control for altitude and pitching motion of the blimp in the longitudinal plane. Some simulations and experiments for a 12m class outdoor blimp are performed to confirm the usefulness of the proposed method.

scholarly journals Optimal Path Following for Differentially Flat Robotic Systems Through a Geometric Problem Formulation

2014 ◽  
Vol 30 (4) ◽  
pp. 980-985 ◽  
Author(s):  
Wannes Van Loock ◽  
Goele Pipeleers ◽  
Moritz Diehl ◽  
Joris De Schutter ◽  
Jan Swevers
Keyword(s):  
Optimal Path ◽  
Path Following ◽  
Problem Formulation ◽  
Robotic Systems ◽  
Geometric Problem

Leg kinematic analysis and prototype experiments of walking-operating multifunctional hexapod robot

2013 ◽  
Vol 228 (12) ◽  
pp. 2217-2232 ◽  
Author(s):  
Pan Yang ◽  
Feng Gao
Keyword(s):  
Kinematic Analysis ◽  
Kinematic Model ◽  
Form Solution ◽  
Spherical Joint ◽  
Universal Joint ◽  
Step Size ◽  
Work Space ◽  
Prismatic Joint ◽  
Forward Kinematic ◽  
Close Form

This paper presents kinematic analysis of a 3-degree of freedom parallel mechanism for hexapod walking-operating multifuctional robot. Each leg of the robot consists of three limbs: universal joint – prismatic joint chain (1-UP) and universal joint – prismatic joint – spherical joint chain (2-UPS) and at the end of the leg there is passive spherical joint to adjust to the uneven ground. In this paper, first the forward kinematic model is built and it shows that the model has close-form solution. Then the work space is discussed in which the robot feet trajectories can be projected. It can be shown that the current trajectories of the feet only take very small work space. After that force analysis is performed and the results show that the payload capability of the mechanism is very high. Experiments of the prototype show that the robot can walk easily with more than 150 kg loads while the step size is more than 0.5 m.

scholarly journals Estimation of soil nitrate in the spring as a basis for adjustment of nitrogen fertiliser rates

2000 ◽  
Vol 9 (1) ◽  
pp. 71-77 ◽  
Author(s):  
J. SIPPOLA
Keyword(s):  
Root Zone ◽  
Nitrate Concentration ◽  
Small Deviation ◽  
Coefficient Of Determination ◽  
Nitrate Content ◽  
Maximum Deviation ◽  
Soil Nitrate ◽  
Mean Values ◽  
Nitrogen Fertiliser ◽  
The Mean

The performance of SOILN model, which simulates soil nitrogen dynamics, was evaluated in respect to its ability to predict nitrate content in soil in spring when growing barley. The data obtained in three year nitrogen fertiliser experiments on different soil types was used. Model was parametrised using the data of the first experimental year and validation results obtained in following years are presented. The results of the simulations of the springtime nitrate in the root zone showed a reasonably small deviation from the measured values. The coefficient of determination, R2 = 0.56 was significant. The regression equation was y = 4 + 0.66x where the constant term was not significantly different from zero and the slope deviated from zero. The mean value of measured nitrate in the root zone in spring was 16 kg/ha and that from the simulation was 15 kg/ha showing that the mean values were close to each other. The mean of deviations between measured and simulated values was 4 kg/ha and the maximum deviation 9 kg/ha. It is concluded that simulation estimated springtime soil nitrate concentration with reasonable confidence that further testing of estimating soil nitrate concentration in spring for adjustment of nitrogen fertilisation using SOILN model should be continued.;

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