Exploiting Null Space in Aerial Manipulation through Model-In-The-Loop Motion Planning

Author(s):  
Antun Ivanovic ◽  
Marko Car ◽  
Matko Orsag ◽  
Stjepan Bogdan
Author(s):  
Shangdong Gong ◽  
Redwan Alqasemi ◽  
Rajiv Dubey

Motion planning of redundant manipulators is an active and widely studied area of research. The inverse kinematics problem can be solved using various optimization methods within the null space to avoid joint limits, obstacle constraints, as well as minimize the velocity or maximize the manipulability measure. However, the relation between the torques of the joints and their respective positions can complicate inverse dynamics of redundant systems. It also makes it challenging to optimize cost functions, such as total torque or kinematic energy. In addition, the functional gradient optimization techniques do not achieve an optimal solution for the goal configuration. We present a study on motion planning using optimal control as a pre-process to find optimal pose at the goal position based on the external forces and gravity compensation, and generate a trajectory with optimized torques using the gradient information of the torque function. As a result, we reach an optimal trajectory that can minimize the torque and takes dynamics into consideration. We demonstrate the motion planning for a planar 3-DOF redundant robotic arm and show the results of the optimized trajectory motion. In the simulation, the torque generated by an external force on the end-effector as well as by the motion of every link is made into an integral over the squared torque norm. This technique is expected to take the torque of every joint into consideration and generate better motion that maintains the torques or kinematic energy of the arm in the safe zone. In future work, the trajectories of the redundant manipulators will be optimized to generate more natural motion as in humanoid arm motion. Similar to the human motion strategy, the robot arm is expected to be able to lift weights held by hands, the configuration of the arm is changed along from the initial configuration to a goal configuration. Furthermore, along with weighted least norm (WLN) solutions, the optimization framework will be more adaptive to the dynamic environment. In this paper, we present the development of our methodology, a simulated test and discussion of the results.


Author(s):  
Imre J. Rudas*and Leon Zlajpah** ◽  

In engineering practice we often have to deal with complex systems, where the conventional approaches for understanding and predicting the behavior of the system can prove to be inadequate. Hence, the researchers try to put some intelligence into the system. The term intelligence in this context still more or less remains a mysterious phenomenon and can be characterized by different abilities of the system or machine, such as adaptation, decision-making, learning, recognition, diagnostics, autonomy, etc. Many of the new results related to this area are published in Journals and in International Conference Proceedings. One such conference is the "IEEE International Conference on Intelligent Engineering Systems". The fourth conference in this series (INES 2000) took place in Portoroz, Slovenia, on September 17-19,2000. There were around eighty participants from eighteen countries around the world. We are glad that so many authors have contributed to ideas related to the issues at the conference. Many of the papers were about applications and design, and others on more theoretical aspects of intelligent systems. This variety made the selection of papers for this special issue very difficult. Eight papers have been selected in the end, which cover different aspects of intelligent engineering systems. It should be pointed out that the respective authors were also kind to revise and update the presented papers for this special issue. The first paper deals with the manipulation problem where the motion changes depending on the state of the system as it is the case in the finger gaiting applications. To solve it the semi-stratified control theory using smooth motion planning is used. The proposed concept combines the stratified motion planning with the unconstrained finger allocations. In the second paper a special branch of Soft Computing developed for the control of mechanical devices is described. It reduces the number of free parameters and computational complexity. For illustration of the efficiency of the proposed adaptive control, a simulation of polishing with a 3 DOF robot is given. The next paper discusses the force control of redundant robots in an unstructured environment. A special attention is given to the decoupling of the task space and null space motion. For that the minimal null space approach is used. The proposed impedance controller assures good task space performances and minimizes the disturbances caused by obstacles. The performance of the proposed controllers has been evaluated by the simulation and by experiments on a real robot. The forth paper presents some advanced modeling approaches and methods. As one of the key issues a manufacturing process model fully associative with form feature based part model has been introduced. The motivation has been that the low level integration of design and manufacturing of mechanical parts, as identified by the authors, is still a main drawback of efficient application of expensive modeling systems. The proposed method allows for creating part model simultaneously with their analysis of machineability. The next paper discusses the design of fractal-order discrete-time controllers. Some approaches to implement fractal derivatives and integrals are analyzed. As the application of the theory of fractional calculus is rather new, many aspects remain to be investigated. The sixth paper demonstrates how to map classical dictionaries and similar structured data to a hypertext structure that is more suitable for the modern media. To achieve the new shape automatically, the HiLog language is used. The automated mapping is illustrated by an example based on Oxford Dictionary of Modern English. In the seventh paper a humanoid robotics shoulder is compared to the human shoulder. First, the capabilities of the robotics shoulder are analyzed and next, using the optical measurement system the human shoulder movements have been measured and analyzed. The last paper discusses the bias-variance tests on multi-layer perception. The performance of Bayesian neural networks is compared with the performance of neural networks trained with a gradient method. Additionally, it is analyzed if it is possible to use a number of networks in committee trained with gradient descent to achieve the performance of a Bayesian network.


2021 ◽  
Vol 18 (3) ◽  
pp. 172988142110122
Author(s):  
Yanhui Wei ◽  
Yongkang Hou ◽  
Shanshan Luo ◽  
Qiangqiang Li ◽  
Jishun Xie

The underwater vehicle-manipulator systems (UVMS) face significant challenges in trajectory tracking and motion planning because of external disturbance (current and payload) and kinematic redundancy. Former algorithms can finish the tracking of end-effector (EE) and free of singularity redundancy solution alone. However, only a few analytical studies have been conducted on coordinated motion planning of UVMS considering the dynamics controller. This article introduces a combined dynamics and kinematics networked fuzzy task priority motion planning method to solve the above problems. It avoids the assumption of perfect dynamic control. Firstly, to eliminate the kinematics error, a dynamic transformation method from joint space to task space is proposed. Without chattering, an outer loop sliding mode controller is designed for tracking EE’s trajectory. Further, to ensure the underwater vehicle’ posture stability and joint constraint, a task priority frame with kinematics error is used to planning the coordinated motion of UVMS, in which the posture and joint limits map into the null space of prioritized tasks, and weight gains are adopted to guarantee orthogonality of secondary tasks. On top of that, the gain weighted are updated by the networked fuzzy logic. The proposed algorithm achieves better coordinated motion planning and tracking performance. Effectiveness is validated by numerical simulation.


Author(s):  
Maciej Michałek ◽  
Krzysztof Kozłowski

Motion planning and feedback control for a unicycle in a way point following task: The VFO approachThis paper is devoted to theway point followingmotion task of a unicycle where the motion planning and the closed-loop motion realization stage are considered. Theway point followingtask is determined by the user-defined sequence of way-points which have to be passed by the unicycle with the assumed finite precision. This sequence will take the vehicle from the initial state to the target state in finite time. The motion planning strategy proposed in the paper does not involve any interpolation of way-points leading to simplified task description and its subsequent realization. The motion planning as well as the motion realization stage are based on the Vector-Field-Orientation (VFO) approach applied here to a new task. The unique features of the resultant VFO control system, namely, predictable vehicle transients, fast error convergence, vehicledirecting effecttogether with very simple controller parametric synthesis, may prove to be useful in practically motivated motion tasks.


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