Thanh Nho Do

Adaptive control of position compensation for Cable-Conduit Mechanisms used in flexible surgical robots

Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a method that allows for performing complex operations via natural orifices without skin incisions. Its main tool is a flexible endoscope. Cable-Conduit Mechanisms (CCMs) are often used in NOTES because of its simplicity, safety in design, and easy transmission. Backlash hysteresis nonlinearities between the cable and the conduit pose difficulties in the motion control of the NOTES system. It is challenging to achieve the precise position of robotic arms when the slave manipulator inside the humans body. This paper presents new approaches to model and control for pairs of CCMs. It is known that the change of cable-conduit configuration will affect the backlash hysteresis non-linearities. To deal with such change, a new nonlinear and adaptive control scheme will be introduced. The backlash hysteresis parameters are online estimated under the assumption of availability of output feedback and unknown bound of nonlinear parameters. To validate the proposed approach, a prototype of single-DOF-Master-Slave system, which consists of a master console, a telesurgical workstation, and a slave manipulator, is also presented. The proposed compensation scheme is experimentally validated using the designed system. The results show that the proposed control scheme efficiently improves the tracking performances of the system regardless of the change of endoscope configuration.

Dynamic Friction-Based Force Feedback for Tendon-Sheath Mechanism in NOTES System

Tendon-sheath mechanism (TSM) is commonly used in flexible endoscopic systems because of its high flexibility, light weight, and easy transmission. Due to the size constraints and sterilization problems, traditional sensors cannot be placed at the tool tips of robotic arms. In addition, nonlinear friction and backlash hysteresis cause many challenges to predict the desired force when the system inside the humans body. It is extremely difficult to provide the force information to haptic devices and subsequently to the users. In this paper, a new scheme of dynamic friction model for a pair of TSMs is proposed to estimate the force at distal end of endoscopic system. In comparison with current approaches in the literature, our model is able to provide continuous force information. The model is able to predict distal force with any sheath shapes. An experimental setup is designed to measure the friction force in the TSM. Finally, the validity of the proposed model approach is confirmed with a good agreement between the estimated values and real experimental data.

Nonlinear Modeling and Parameter Identification of Dynamic Friction Model in Tendon Sheath for Flexible Endoscopic Systems

Minimally Invasive Surgery (MIS) has established a revolution in surgical communities, with its many advantages over open surgery. The need of more simplicity and high maneuverability makes the tendon sheath a very suitable mechanism in flexible endoscopic systems. Due to the restriction on size constraints and sterilization problems, traditional sensors cannot be mounted on the tool tips of a slave manipulator. Moreover, in the presence of nonlinear friction and hysteresis between the tendon and the sheath, it is extremely difficult to control the precise motion and sense the force during the operation. This paper proposes a new dynamic friction model to estimate the force at the end effector for the tendon sheath mechanism. The proposed friction model can adapt with any initial pretension of the tendon and any configuration of the sheath. The nonlinearities in both sliding and presliding regimes can be captured by using an internal state variable and functions dependent velocity and acceleration. A specific setup has been designed in order to measure the friction force between the tendon and the sheath. Finally, the validity of the identified model is confirmed by a good agreement of its prediction and experimental data.

Position Control of Asymmetric Nonlinearities for a Cable-Conduit Mechanism

Cable-conduit mechanism (CCM) is widely used in robotic hands, rescue robots, rehabilitation robots, and surgical robots because it offers efficient transmission of forces/torques from the external actuator to the end effector with lightweight 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. 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 approximation-based robust control laws, which have the capabilities of estimating unknown system parameters, are also established. In addition, the deigned 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 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.

Development and Testing of a Magnetically Actuated Capsule Endoscopy for Obesity Treatment

Intra-gastric balloons (IGB) have become an efficient and less invasive method for obesity treatment. The use of traditional IGBs require complex insertion tools and flexible endoscopes to place and remove the balloon inside the patient’s stomach, which may cause discomfort and complications to the patient. This paper introduces a new ingestible weight-loss capsule with a magnetically remote-controlled inflatable and deflatable balloon. To inflate the balloon, biocompatible effervescent chemicals are used. As the source of the actuation is provided via external magnetic fields, the magnetic capsule size can be significantly reduced compared to current weight-loss capsules in the literature. In addition, there are no limitations on the power supply. To lose weight, the obese subject needs only to swallow the magnetic capsule with a glass of water. Once the magnetic capsule has reached the patient’s stomach, the balloon will be wirelessly inflated to occupy gastric space and give the feeling of satiety. The balloon can be wirelessly deflated at any time to allow the magnetic capsule to travel down the intestine and exit the body via normal peristalsis. The optimal ratio between the acid and base to provide the desired gas volume is experimentally evaluated and presented. A prototype capsule (9.6mm x 27mm) is developed and experimentally validated in ex-vivo experiments. The unique ease of delivery and expulsion of the proposed magnetic capsule is slated to make this development a good treatment option for people seeking to lose excess weight.

Design and Control of a Mechatronic Tracheostomy Tube for Automated Tracheal Suctioning

Goal: Mechanical ventilation is required to aid patients with breathing difficulty to breathe more comfortably. A tracheostomy tube inserted through an opening in the patient neck into the trachea is connected to a ventilator for suctioning. Currently, nurses spend millions of person-hours yearly to perform this task. To save significant person-hours, an automated mechatronic tracheostomy system is needed. This system allows for relieving nurses and other carers from the millions of person-hours spent yearly on tracheal suctioning. In addition, it will result in huge healthcare cost savings. Methods: We introduce a novel mechatronic tracheostomy system including the development of a long suction catheter, automatic suctioning mechanisms, and relevant control approaches to perform tracheal suctioning automatically. To stop the catheter at a desired position, two approaches are introduced: 1) Based on the known travel length of the catheter tip; 2) Based on a new sensing device integrated at the catheter tip. It is known that backlash nonlinearity between the suction catheter and its conduit as well as in the gear system of the actuator are unavoidable. They cause difficulties to control the exact position of the catheter tip. For the former case, we develop an approximate model of backlash and a direct inverse scheme to enhance the system performances. The scheme does not require any complex inversions of the backlash model and allows easy implementations. For the latter case, a new sensing device integrated into the suction catheter tip is developed and backlash compensation controls are avoided. Results: Automated suctioning validations are successfully carried out on the proposed experimental system. Comparisons and discussions are also introduced. Significance: The results demonstrate a significant contribution and potential benefits to the mechanical ventilation areas.Goal: Mechanical ventilation is required to aid patients with breathing difficulty to breathe more comfortably. A tracheostomy tube inserted through an opening in the patient neck into the trachea is connected to a ventilator for suctioning. Currently, nurses spend millions of person-hours yearly to perform this task. To save significant person-hours, an automated mechatronic tracheostomy system is needed. This system allows for relieving nurses and other carers from the millions of person-hours spent yearly on tracheal suctioning. In addition, it will result in huge healthcare cost savings. Methods: We introduce a novel mechatronic tracheostomy system including the development of a long suction catheter, automatic suctioning mechanisms, and relevant control approaches to perform tracheal suctioning automatically. To stop the catheter at a desired position, two approaches are introduced: 1) Based on the known travel length of the catheter tip; 2) Based on a new sensing device integrated at the catheter tip. It is known that backlash nonlinearity between the suction catheter and its conduit as well as in the gear system of the actuator are unavoidable. They cause difficulties to control the exact position of the catheter tip. For the former case, we develop an approximate model of backlash and a direct inverse scheme to enhance the system performances. The scheme does not require any complex inversions of the backlash model and allows easy implementations. For the latter case, a new sensing device integrated into the suction catheter tip is developed and backlash compensation controls are avoided. Results: Automated suctioning validations are successfully carried out on the proposed experimental system. Comparisons and discussions are also introduced. Significance: The results demonstrate a significant contribution and potential benefits to the mechanical ventilation areas.

A Magnetic Soft Endoscopic Capsule-Inflated Intragastric Balloon for Weight Management.

Overweight and obesity have been identified as a cause of high risk diseases like diabetes and cancer. Although conventional Intragastric Balloons (IGBs) have become an efficient and less invasive method for overweight and obesity treatment, the use of conventional tools such as catheter or endoscope to insert and remove the IGBs from the patient’s body causes nausea, vomiting, discomfort, and even gastric mucous damage. To eliminate these drawbacks, we develop a novel magnetic soft capsule device with gas-filled balloon inflation. The balloon is made from a thin and biocompatible material that can be inflated to a desired volume using biocompatible effervescent chemicals. In addition, both the outer balloon and inner capsule are designed to be soft and chemical resistance. The soft capsule shell is fabricated using scaffold-solvent approach while the outer balloon utilizes a novel fabrication approach for 3D spherical structure. A prototype of the proposed capsule and balloon is given. Experiments are successfully carried out in stimulated gastric environment and fresh porcine stomach to validate the effectiveness and reliability of the proposed approach.

Design and control of a novel mechatronic tracheostomy tube-inserted suction catheter for automated tracheal suctioning

Mechanical ventilation is required to aid patients with breathing difficulty to breathe more comfortably. A tracheostomy tube is inserted through an opening in the patient neck into the trachea, below the vocal cords. This opening is either created surgically or using a percutaneous dilatational technique. The inserted tube sits in the trachea, above the carina, and before the airways branch into the left and right main bronchi. In mechanical ventilation, the tube is connected to a ventilator and air is moved in and out of the lungs via positive pressure. In this process, mucus will accumulate at the point of branching into the branchi. Currently, this mucus is manually removed half-hour by inserting a suction tube via the tracheostomy to reach the point of branching. Nurses spend millions of person-hours to perform this task yearly. To save significant person-hours, an automated system is needed. This system also allows the patient to recover at home, rather stay in hospital solely for nurses to remove mucus periodically. In this paper, we present a novel mechatronic device to perform automatic tracheal suctioning in conjunction with a tracheostomy tube. A new suctioning catheter is also developed. It is known that nonlinear friction and backlash between the suctioning catheter and its conduit as well as in the gear system of the actuator cause difficulties to accurately control the position of catheter tip. To enhance the system performances, a novel direct inverse of backlash-like hysteresis model-based feedforward is also developed. The designed device and proposed compensation scheme are experimentally validated. The results demonstrate a significant contribution and potential benefits to the mechanical ventilation works.

Adaptive Tracking Approach of Flexible Cable Conduit-Actuated NOTES Systems for Early Gastric Cancer Treatments

To control robotic arms mounted on a flexible endoscope in Natural Orifice Transluminal Endoscopic Surgery (NOTES) procedure, Cable-Conduit Mechanisms (CCMs) are often used. Although the CCMs offer simplicity, safety, and easy transmission, nonlinear friction and backlash-like hysteresis between the cable and the conduit introduce some difficulties in the motion control of the NOTES system. It is challenging to achieve the precise position of robotic arms and force feedback information when the slave manipulator is inside the humans body. This paper presents the dynamic transmission characteristics of CCMs and control strategies to compensate for achieving precise position tracking of the robotic arms. The cable-conduit tension and position transmission are analysed and discussed for both sliding and presliding regimes. Unlike current approaches in the literature, position transmission of the CCM is modelled by an approximation of backlash-like hysteresis profile for both loading and unloading phases. In addition, nonlinear adaptive control algorithm is also used to enhance the tracking performance for a pair of CCMs regardless of the change of cable-conduit configuration during the operation. The backlash-like hysteresis parameters are online estimated under an assumption of presence of output feedback and unknown bound of nonlinear parameters. To validate the proposed approach, a prototype of single-DOF-flexible robotic system, which consists of a motion control device, a telesurgical workstation, and a slave manipulator, is also developed. The proposed compensation scheme is experimentally validated using the designed system. The results show that the proposed control scheme improves the tracking performances significantly regardless of the change of endoscope configuration.