Minh Tu Pham

Sensor-based guidance control of a continuum robot for a semi-autonomous colonoscopy

Due to their compliance and high dexterity, biologically-inspired continuum robots have attracted much interest for applications such as medical surgery, urban search and rescue, de-mining etc. In this paper, we will present an application to medical surgery-colonoscopy by designing a pneumatic-driven flexible robotic manipulator, called ColoBot. The focus of this paper lies in the sensor-based position control of the ColoBot for guiding the advancement in a tubular, compliant and slippery environment. The kinematic model related the position of the distal end of the ColoBot to the actuator inputs which is firstly developed and formulated to control the shape of the ColoBot through position control of the distal tip. To achieve safe guidance, the ideal position of the tip should be in the central axis of the colon. A method based on a circumscribed circle is proposed to approximate the central position in real-time based on three sensor readings. This position will be used as reference position for the tip to adjust its shape in real time to avoid the contact with tube wall. This proposed approach can be extended to the control of continuum robots in the conditions of a dynamically confined space. The simulation results and experimental results with a curved tube will be presented in order to validate the proposed control strategy.

Identification of joint stiffness with bandpass filtering

Proposes a method to identify the joint stiffness of a robot using a bandpass filter. It is based on moving one axis at a time. The dynamic model reduces to a model which is linear in relation to a minimum set of dynamical parameters which have to be identified. These parameters are estimated using the least squares solution of an over determined linear system obtained from the sampling of the dynamic model along a closed loop tracking trajectory. Conditions for a good data processing before identification are exhibited through practical aspects concerning data sampling and data filtering. An experimental study shows the efficiency of the method with two sets of data depending on motor joint position measurements.

A new mechanical birth simulator: BirthSIM

This paper deals with a new mechanical birth simulator (BirthSIM). Currently available birth simulators provide manikins that include new-born head and maternal pelvis but they do not produce the movements of the new-born in the mothers pelvis. Furthermore available maternal pelvis do not include interface pressure and are not enough realistic to simulate maternal pelvic muscles. In summary, these simulators do not help students to practice the gestures they should safely use to help the new-born in normal and at-risk situations of delivery. The originality of our mechanical birth simulator, is to provide a system to mimic the last step of the instrumental delivery, to insure a safe training of junior obstetricians and to test new techniques in obstetrics practice. The new mechanical birth simulator is composed of three parts: a physical new-born head and a maternal pelvis manikin, an interface pressure system, and a pneumatic actuator that develops an active resistance. Driven by a computer, the simulator can simulate the contractions, the interface pressure applied in the new-born head and mimic birth complications.

Assessment of forceps blade orientations during their placement using an instrumented childbirth simulator

This paper aims to highlight the benefits of simulator training in obstetric manipulations such as forceps blade placement. The BirthSIM simulator is used to mimic operative vaginal deliveries. To characterise forceps blade placement, we studied the curvature of forceps path. The orientation of the forceps blades are studied in the quaternion unit space to ensure time‐independent analysis. The results showed progress for all novices in forceps blade placement. Simulator training helps them to develop their self‐confidence and acquire experience before working in the delivery room.

Does forceps training on a birth simulator allow obstetricians to improve forceps blade placement

OBJECTIVE The aim of this study was to evaluate whether forceps training on a birth simulator allows obstetricians to improve forceps blade placement. STUDY DESIGN Analysis was based on 600 forceps blade placements performed by ten trainees on a simulator. The trajectories used by the trainees were assessed using reference spheres that reflected an optimal bimalar placement. Three definitions of success were used: small-sphere success, medium-sphere success and large-sphere success were respectively defined by the forceps blade tip being within 5, 10 or 15mm of the center of the sphere (the small-sphere being nested within the medium-sphere and the small and medium being nested within the large-sphere). Wilcoxon paired analysis was performed to compare the first (50 trajectories) and final (50 trajectories) sets of five forceps placements. Graphical representation and linear regression were used to visualize the learning process. RESULTS 596 trajectories were available for analysis. During the last set of five forceps the success rate was respectively 28%, 72% and 86% for small-sphere, medium-sphere and large-sphere success with the right blade and 8%, 32% and 70% for the left blade. Wilcoxon analysis showed a highly significant improvement for all kinds of success in the right blade and for large-sphere success in the left blade. Linear regression slopes were significant. Using a projection, the theoretical numbers of placements needed to achieve a 100% success rate for small-sphere, medium-sphere and large-sphere were respectively 80, 45 and 35. CONCLUSION These results strongly suggest that performing forceps blade placement on birth simulator allows obstetricians to improve their skills.

Sliding mode control of a pneumatic haptic teleoperation system with on/off solenoid valves

This paper presents a novel bilateral control scheme for pneumatic teleoperation systems that are actuated by low-cost solenoid valves. A sliding mode control is incorporated into a two-channel, bilateral teleoperation architecture involving position-position, force-force, or force-position schemes. An analysis of stability and transparency of the closed-loop teleoperation system is carried out. The proposed control design is verified on a single-degree-of-freedom pneumatic teleoperation system with four on/off solenoid valves. Moreover, simulation results demonstrate high accuracies in terms of position and force tracking in the teleoperation system.

Bilateral Control of Nonlinear Pneumatic Teleoperation System With Solenoid Valves

In past research on the control of pneumatic actuators, typically proportional servovalves have been used for achieving high-performance control of the mass flow rate. In this brief, we instead use fast-switching ON/OFF valves due to their distinct advantages in terms of low cost and small size. Accurate control of pneumatic actuators with ON/OFF solenoid valves is a challenge since the system dynamics is both discrete input and highly nonlinear. In this brief, we apply a hybrid control algorithm to a pneumatic actuator with ON/OFF valves. Such a control approach is developed for choosing the best control vector at each sample time to track the reference state (i.e., desired force) in the inner force control loop within a bilateral teleoperation system. Experimental results show that good teleoperation transparency is achieved despite all the obstacles such as discrete input and nonlinear behavior of the pneumatic-actuated teleoperation system.

Design and Modeling of an Upper Extremity Exoskeleton

This paper presents the design and modeling results of an upper extremity exoskeleton mounted on a wheel chair. This new device is dedicated to regular and efficient rehabilitation training for weak and injured people without the continuous presence of a therapist. The exoskeleton being a wearable robotic device attached to the human arm, the user provides information signals to the controller in order to generate the appropriate control signals for different training strategies and paradigms. This upper extremity exoskeleton covers four basic degrees of freedom of the shoulder and the elbow joints with three additional adaptability degrees of freedom in order to match the arm anatomy of different users.

Modeling, simulation and control of high speed machine tools using robotics formalism

This paper deals with the modeling, simulation and numerical control of high speed machine tool axes. A new way of modeling is introduced by using the description of robotic manipulators. The dynamics of rigid bodies, the elasticity of the bodies and the mechanical transmission, the dynamics and saturations of the electric actuators, the effect of the numerical control as delays and quantization are considered for the simulation. The cascade PI speed loop and P position loop controller is designed using a frequency approach and an optimization procedure taking into account the lumped model and the effects of digital control. An experimental validation on real machine tool axis is presented and compared with the simulated results.

A new learning method for obstetric gestures using the BirthSIM simulator

Today, medical simulators are increasingly gaining attraction in clinical settings. These tools allow physicians to visualize the positions of organs, plan surgical interventions, and carry out more comprehensive post operative monitoring. A childbirth simulator provides a risk-free training and research tool for comparing various techniques that use obstetrical instruments or validating new methods. This paper presents a new teaching method to place forceps blades for obstetricians using an instrumented childbirth simulator. The proposed method is based on a physical simulator coupled with a computer graphics interface. Another aspect of this paper is to provide understanding marks to quantify the progression during a training. A first one allows to study the path in space and to quantify their repeatability, a second one allows to compute the error to a reference gesture defined by an expert. Both marks are complementary. Two novices were trained and they manage to have a more repeatable gesture and above all to become closer to a reference gesture, i.e. to reduce the injury linked to the use of forceps during instrumental deliveries.