Richard Gourdeau

Real-Time MRI-Based Control of a Ferromagnetic Core for Endovascular Navigation

This paper shows that even a simple proportional-integral-derivative (PID) controller can be used in a clinical MRI system for real-time navigation of a ferromagnetic bead along a predefined trajectory. Although the PID controller has been validated in vivo in the artery of a living animal using a conventional clinical MRI platform, here the rectilinear navigation of a ferromagnetic bead is assessed experimentally along a two-dimensional (2D) path as well as the control of the bead in a pulsatile flow. The experimental results suggest the likelihood of controlling untethered microdevices or robots equipped with a ferromagnetic core inside complex pathways in the human body.

Object-oriented programming for robotic manipulator simulation

Using an object-oriented programming approach, ROBOOP, a robotic manipulator simulation package which is both platform and vendor independent, compares favourably against a package requiring similar coding effort. Performance tests show that with ROBOOP the class inverse dynamics of a 6-DOF robot can be computed in less than 5 ms with a Pentium 100 MHz computer.

The potential impact of intelligent power wheelchair use on social participation: perspectives of users, caregivers and clinicians

Abstract Purpose: To explore power wheelchair users’, caregivers’ and clinicians’ perspectives regarding the potential impact of intelligent power wheelchair use on social participation. Methods: Semi-structured interviews were conducted with power wheelchair users (n = 12), caregivers (n = 4) and clinicians (n = 12). An illustrative video was used to facilitate discussion. The transcribed interviews were analyzed using thematic analysis. Results: Three main themes were identified based on the experiences of the power wheelchair users, caregivers and clinicians: (1) increased social participation opportunities, (2) changing how social participation is experienced and (3) decreased risk of accidents during social participation. Conclusion: Findings from this study suggest that an intelligent power wheelchair would enhance social participation in a variety of important ways, thereby providing support for continued design and development of this assistive technology. Implications for Rehabilitation An intelligent power wheelchair has the potential to: Increase social participation opportunities by overcoming challenges associated with navigating through crowds and small spaces. Change how social participation is experienced through “normalizing” social interactions and decreasing the effort required to drive a power wheelchair. Decrease the risk of accidents during social participation by reducing the need for dangerous compensatory strategies and minimizing the impact of the physical environment.

Adaptive control of robotic manipulators: experimental results

An adaptive motion control scheme for robotic manipulators is presented. This is an adaptive computed torque method (CTM) that requires only position measurements. These measurements and the input torques are used in an extended Kalman filter (EKF) to estimate the inertial parameter of the full nonlinear robot model as well as the joint positions and velocities. These estimates are used by the CTM to generate the input torques. This combination of the EKF and the CTM was shown to result in a stable adaptive control scheme. Experimental results with a two-degree-of-freedom direct-drive robot illustrate the performance of this scheme.<<ETX>>

Bidimensional MRI-based Navigation System Using a PID Controller

The feasibility of using 2D real-time control to navigate ferromagnetic entities in an MRI bore for novel medical interventions is assessed. Preliminary experimental results confirm that a simple PID controller can be suitable for several applications where targeting out-of-reach locations within the cardiovascular system is essential

Computed torque control of robots without joint velocity measurements

We present a robot motion controller that does not require velocity measurements. This controller combines an observer with the computed torque method. The stability of the resulting scheme is shown. The computational simplicity of the scheme is one of its advantages. Experimental results are presented to illustrate the performance of the scheme when measurement noise is present.

Parameter identification of a semi-flexible kinematic model for serial manipulators

Structural and control flexibilities affect the absolute precision of serial manipulators. A semi-flexible kinematic model is developed, to improve the absolute static precision. It expands the solid body model by incorporating a spring effect for each joint and a beam effect for each link. The identifiability of the added parameters and the effect of measurement noise are explored on a R4 robot. It requires efforts and pose errors to be known in the tool frame only. Simulation results show that identification of some of the parameters is sensitive to measurement noise on forces and pose. In fact, joint flexibility displacement and beam flexion that occur in the same plane are difficult to dissociate in noisy condition. However, a subset of the original parameters can be defined leading to a model that can be more accurately identified when measurement noise is present. In simulation, precompensation is used in an inverse semi-flexible model that results in a 98% decrease of pose error compared to the rigid body inverse geometric model.

Robust control of a launch vehicle in atmospheric ascent based on guardian maps

A robust control design for a space launcher during its atmospheric ascent is presented. Considering a typical wind profile during flight, the launcher controller has to first stabilize the open-loop unstable system, and then maintain verticality. The model available takes into account flexible modes and nozzle actuator dynamics, and is time-variant. Aside from launcher stability, additional requirements pertaining to frequency and damping of rigid launcher modes as well as flexible ones, must be fulfilled. The synthesis relies on guardian maps, making possible to characterize the sets of all controller gains which meet the requirements, by specifying areas of interest where the systems closed-loop poles must be located.

COOPERATIVE ROBOTIC SYSTEM USING DISTRIBUTED DECISION MECHANISMS WITH DELIBERATIVE CENTRAL SUPERVISOR

Cooperative multi-robot systems with distributed decision mechanisms and distributed sensing may be the source of decisional conflicts which can lead to severe performance deterioration. A deliberative central supervisor is a simple approach to correct any incoherent decisions in the system. Given an application, the supervisor can be an autonomous software agent or a human-machine interface. Using Hierarchical Decision Machines (HDM) as distributed decision mechanisms, the decision supervision can use simple matrix representations of decisional data. The resulting architecture has been tested on a fully autonomous team of soccer-playing robots and results indicate that it is well adapted for, but not restricted to, the specific needs of autonomous multi-robot systems with real-time distributed sensing and decision taking.

Dual conformance index‐based robotic arm placement and adaptation

A method to decide the placement and structural adaptation of a robotic arm with respect to a set of tasks is presented. Commercialized CAD/CAM tools mostly limit the layout criterion of robotized cells to the reachability of a task. They furnish little assistance for the selection of the tool, the arm, or its placement. A robot-task conformance index is shown to overcome these limitations. Four volume ratios define the index. They are taken over a robot ellipsoid, a task constraints ellipsoid, and a minimum containing and a maximum contained ellipsoid. The strict equivalence of the four ratios is proven. A dual computational sequence and the concept of relevant singularities are introduced. This dual computation is shown to equal the original conformance index outside relevant singularities. The index is applied to cases of increasing difficulty. Internal motions of joints within the null space of the Jacobian are typically used to maximize the index. The cases of simultaneous multitask optimization, tool definition, and robotic structure definition are addressed. Its usefulness for the design of the cell layout is exemplified.