Energy-based MOR for Flexible Space Robotic Systems

Abrasion and blunt tissue trauma study of a novel flexible robotic system in the porcine model

In this chapter, a planar two-bar space robot is taken as the research object, and the dynamics equations of fully rigid and joint flexible space robot systems are derived by using momentum conservation and Lagrange equation of the second kind. Aiming at flexible joint space robot system, the system is decomposed into fast and slow subsystems based on singular perturbation. Considering the friction characteristics of joints, a robust controller based on the friction upper bound was designed to offset the influence of friction torque and improve the flat roof phenomenon in joint trajectory tracking control. For flexible joint space robot system, a fast variable subsystem controller is designed using moment differential to actively suppress flexible vibration. The controller of slow subsystem is designed by robust method and a bounded friction compensation term is introduced to offset the influence of joint friction torque. The effectiveness of the proposed manipulator control scheme is verified by numerical simulation experiments.

Cable-conduit mechanism (CCM) or tendon-sheath mechanism (TSM) is widely used in many flexible robotic systems such as prosthetic hand robots, rehabilitation robots, and surgical robots because it offers efficient transmission of forces/torques from the external actuator to the end effector with light weight and high flexibility. However, the accurate position control is challenging in such mechanism due to friction and backlash-like hysteresis between the cable and the conduit. In this paper, a new control approach is proposed to enhance the trajectory tracking performances of the CCM using in flexible robotic systems. Unlike current approaches for the CCM in the literature, the proposed scheme considers the position transmission of the CCM as an approximation of backlash-like hysteresis nonlinearities without requiring the exact values of model parameters and their bounds. Online estimation of unknown system parameters are also established. In addition, the designed controller can adapt to any changes of the cable-conduit configuration and it is stable. The results of the proposed control techniques have been experimentally validated on a real flexible robotic system using a flexible endoscope. Experimental validations show substantial improvements on the performances of position tracking for the use of CCM regardless of the arbitrary changes of the cable-conduit configurations.

This thesis addresses stable inversion based output tracking control and its applications to robotic systems. It considers the non-causal invertibility (stable inversion) problem of control systems in its various aspects including properties of stable inverses and algorithms for constructing stable inverses. Then, the stable inversion approach is applied to solve a control problem of long-standing interest: output tracking control for non-minimum phase nonlinear systems. A minimum energy property of stable inverses is firstly established. The property claims that given any desired output trajectory, out of infinitely many possible inverse solutions, the one provided by the stable inversion process is the only one that has finite energy. Based on this property, a numerical procedure is developed to provide an efficient approach to construct stable inverses. Secondly, a new output tracking control design is developed. The design incorporates stable inverses and assumes a controller structure of feed-forward plus feedback. It achieves high precision tracking together with closed-loop stability. Furthermore, when system uncertainties are considered and assumed to satisfy the so-called matching conditions, a modified controller structure is presented and the corresponding robust tracking performance is discussed. Finally, the stable inversion based tracking control design is applied to three flexible robotic systems. The first study is output tracking control of a flexible-joint robot. The application demonstrates how the new design deals with the undesirable non-minimum phase property and achieves desired output tracking. The second application is tip trajectory tracking for a two-flexible-link manipulator. This thesis, for the first time, addresses the problem of stable tip trajectory tracking without any transient or steady-state errors for such non-minimum phase systems. In the third application, a new optimal motion control strategy for a flexible space robot is presented. The space robot system is assumed to consist of a two-link flexible manipulator attached to rigid space-craft. Optimality is in the sense that a performance index measured by maneuvering time, control effort, and structural vibrations is minimized while the interference from the manipulator to spacecraft is kept satisfactorily small. Studies on three applications demonstrate that the stable inversion based control design is very effective on output tracking for various robotic systems. This approach is expected to perform equivalently well for many other realistic non-minimum phase nonlinear systems.

Edge intelligence and agnostic robotic paradigm in resource synchronisation and sharing in flexible robotic and facility control system

As manufacturing trends shift towards customized production, the demand for agile automation systems capable of efficient adaptation to rapidly changing task requirements is rising. This work presents a flexible robotic assembly system that combines CAD based component localization, compliance control, and a multi-modal gripper to enable robust and efficient programming of complex tasks. The process can be easily configured for novel assemblies through a dedicated Graphical User Interface (GUI), which facilitates component identification and task sequencing. Component poses are extracted from 3D CAD models in reference to the assembly origin, while the active compliance scheme compensates for minor positioning errors. The gripper incorporates a parallel jaw element, a rotating module, and an electromagnet to minimize retooling delays. The first iteration of the proposed system placed first in the manufacturing track of the Robotic Grasping and Manipulation Competition of the 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), experimentally validating its efficiency.

This paper studies the tracking control problem of a single-link flexible robotic manipulator system with unmodeled dynamics and motion constraint. A dynamic surface control scheme is proposed to design the adaptive controller ensuring both desired tracking performance and constraint satisfaction. A virtual state observer is constructed to estimate the unmeasured state signals. The RBF NNs are used to approximate unknown functions. Dynamic signal and nonlinear mapping are introduced to deal with the dynamic uncertainties and solve motion constraint problem, respectively. A simulation study is presented to verify the effectiveness of the proposed control approach.

The selection of orders is the method of gathering the parts needed to assemble the final products from storage sites. Kitting is the name of a ready-to-use package or a parts kit, flexible robotic systems will significantly help the industry to improve the performance of this activity. In reality, despite some other limitations on the complexity of components and component characteristics, the technological advances in recent years in robotics and artificial intelligence allows the treatment of a wide range of items. In this article, we study the robotic kitting system with a Robotic Mounted Rail Arm System (RMRAS), which travels narrowly to choose the elements. The objective is to evaluate the efficiency of a robotic kitting system in cycle times through modeling of the elementary kitting operations that the robot performs (pick and room, move, change tools, etc.). The experimental results show that the proposed method enhances the performance and efficiency ratio when compared to other existing methods. This study with the manufacturer can help him assess the robotic area performance in a given design (layout and picking a policy, etc.) as part of an ongoing project on automation of kitting operations.

This paper proposes a nonsingular terminal sliding mode control for a two-link flexible manipulator. The flexible robotic system is decomposed into an input-output subsystem and an internal subsystem. A novel inverse dynamics nonsingular terminal sliding mode controller is designed to make the input-output subsystem converge to its equilibrium point in finite time. In order to achieve good performance of zero dynamics of the system, six parameters of the controller are optimized by a genetic algorithm. Furthermore, a bounded convergence region is obtained using Lyapunov stability theory to guarantee the stability of the zero dynamic subsystem with uncertain parameters, which leads to asymptotical stability of the whole flexible manipulator system. Simulation results are presented to validate the design.

Traditionally, most thyroid surgery utilizes a curvilinear cervical incision with a resulting permanent scar. Minimally invasive and remote access thyroid surgery techniques continue to evolve. Transoral approaches through a vestibular incision have been developed at several centers throughout the world, obviating the need for a cutaneous incision and optimizing aesthetics. To date this technique has been performed using rigid endoscopes or a linear robotic platform. The goal of this study was to test the feasibility of a novel flexible robotic system to perform a transvestibular thyroidectomy in a preclinical cadaver model. Preclinical feasibility study. Right and left thyroid lobectomies were successfully performed via a transvestibular approach in four cadavers. A single vestibular incision between bilateral mental nerves allowed entrance of the flexible robot in a subplatysmal plane in both male and female cadavers. The recurrent laryngeal nerves and parathyroids were identified and preserved. The flexible three-dimensional camera allowed excellent visualization and could be easily repositioned for optimal visualization of right and left structures. The flexible and wristed instruments enabled an atraumatic approach and allowed for precise surgical technique. The transoral vestibular approach to the central neck is a promising technique for thyroidectomy with optimal cosmesis and can be successfully accomplished using this novel flexible robotic system. Improvements in visualization and access offered by this system may improve application of this technique. NA Laryngoscope, 129:1482-1487, 2019.

Controlling robot with the mechanical resonance has been receiving increased attention. A new effective control method, a resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for position and force control system. This work presents a new approach to the controlling of flexible robot system by a switching operation mode resonance ratio control. To calculate the optimal parameters of position/force servoing based on resonance ratio control, a Coefficient Diagram Method (CDM) is employed. In this paper, we introduce a novel approach that automatically adapt algorithm parameters conditional based on the operational tasks. Moreover, a multiencoder based disturbance observer (MEDOB) is shown to estimate the external force on the load side, rather than using a force sensor. The experiments with a linear motor and spring show the validity of the approach. From the experiments, it can reject vibration to improve controlling performance.

The use of transanal total mesorectal excision (taTME) for treatment of rectal cancer is growing, but anatomic constraints prevent access to the proximal rectum with rigid instruments. The articulated instrumentation of current surgical robots is promising in overcoming these limitations, but the bulky size of current platforms inhibits the proximal reach of dissection. Flexible robotic systems could overcome these constraints while maintaining a stable platform for dissection. The goal of this study was to evaluate feasibility of performing taTME using the semi-robotic Flex® System (Medrobotics Corp., Raynham, MA) in human cadavers. taTME was performed by two surgeons in six fresh human cadaveric specimens using the Flex® System, with or without transabdominal laparoscopic assistance. Both mid- and low-rectal lesions were simulated. Metrics including quality of visualization, maintenance of pneumorectum, maneuverability of instruments, effectiveness of pursestring suture placement, and dissection in an anatomically correct plane were evaluated. The semi-robotic endoluminal platform allowed for excellent visualization, insufflation, and dissection during taTME. Adequate pursestring occlusion of the rectum was achieved in all six cases. In cadavers with simulated mid-rectal lesions (N = 4), dissection and anterior peritoneal entry was achieved in all cases, with abdominal assistance utilized in two of four cases. In cadavers with simulated low-rectal lesions (N = 2), dissection was incomplete and aborted due to difficulty maneuvering instruments in close proximity to the rigid transanal port. Use of the Flex® system for taTME is feasible for mid-rectal dissection. Advantages over the traditional multi-armed robot include longer reach of instruments with the ability to dissect up to 17cm from the anal verge, as well as tactile feedback. The current design of the flexible platform does not permit safe dissection in the distal rectum, although this constraint may be resolved with future adjustments to the equipment.

Dynamics simulation plays a key role in the design, verification, and operation planning of space manipulator systems because of the difficulties of ground-based physical tests with large, flexible robotic systems. Modeling of contact dynamics has increasingly become an essential step in dynamics simulation of space station robotic operations (such as the assembly and maintenance of the station). This role requires the modeling tool to have very high fidelity. This paper describes a research project aimed at experimentally validating a general contact dynamics simulation software developed by McDonald Dettwiler Space and Advanced Robotics Ltd (previously Spar Aerospace Ltd). The experimental tests were carried out in the robotics laboratory at the University of Victoria. The validation results demonstrated that the software is capable of predicting realistic contact behavior.

The sliding model control problem of distributed parameter system is investigated with frequency domain approach in this paper. Under the conditions more general than in [3] and [4], an equivalent control theorem is proposed and proved. Finally, we apply the equivalent control theorem to a flexible robot system so that the robot arm can be exponentially stable under the sliding model control.

Today in almost every part of our daily life we use some kind of electronic device. Among these devices are e.g, small tools used in the kitchen as well as larger devices like a TV set or a personal computer. Because of the large quantity of such end of life products, an environmentally and economically sensible way to treat this problem must be found. Especially for expensive products containing valuable modules nondestructive disassembly and the possibility to reuse some components seems to be a promising approach. The paper describes research for autonomous disassembly of standard PC hardware. A flexible robot system is realized as a complete experimental setup in our laboratory. This demonstrates achieved abilities in the fields of image analysis and extraction and processing of information for planning of actions as well as flexible control of the disassembly process.