Gianmarc Coppola

Multi-Dimensional MEMS/Micro Sensor for Force and Moment Sensing: A Review

The importance of force sensing technologies was recognized in the 1970s. Since then, multidimensional microelectromechanical systems (MEMS)/micro force/moment (F/M) sensors have permeated a wide variety of products. A multidimensional MEMS/micro-F/M sensor can measure the tangential force terms along x-, y-, and z-axis (Fx, Fy and Fz) as well as the moments terms about x-, y-, and z-axis (Mx, My and Mz) simultaneously with micro-Newton and nano-Newtonmeter resolution. This paper presents an overview of MEMS/micro-F/M sensors. This field is critical to many biomedical applications, materials science, industrial automation, dimension measurements in microcomponents, and nanomanufacturing applications, and has attracted great activity in the past 15-25 years. The evaluation of different F/M sensing principles, recent advances in various designs, and their significance and limitations are analyzed through specific examples. Furthermore, current challenges and new area for future applications of micro-F/M sensing technology have been identified.

Design and Analysis of a Sensor System for Cutting Force Measurement in Machining Processes

Multi-component force sensors have infiltrated a wide variety of automation products since the 1970s. However, one seldom finds full-component sensor systems available in the market for cutting force measurement in machine processes. In this paper, a new six-component sensor system with a compact monolithic elastic element (EE) is designed and developed to detect the tangential cutting forces Fx, Fy and Fz (i.e., forces along x-, y-, and z-axis) as well as the cutting moments Mx, My and Mz (i.e., moments about x-, y-, and z-axis) simultaneously. Optimal structural parameters of the EE are carefully designed via simulation-driven optimization. Moreover, a prototype sensor system is fabricated, which is applied to a 5-axis parallel kinematic machining center. Calibration experimental results demonstrate that the system is capable of measuring cutting forces and moments with good linearity while minimizing coupling error. Both the Finite Element Analysis (FEA) and calibration experimental studies validate the high performance of the proposed sensor system that is expected to be adopted into machining processes.

Design of Parallel Mechanisms for Flexible Manufacturing With Reconfigurable Dynamics

Reconfigurable robotic systems can enhance productivity and save costs in the ever growing flexible manufacturing regime. In this work, the idea to synthesize robotic mechanisms with dynamic properties that are reconfigurable is studied, and a methodology to design reconfigurable mechanisms with this property is proposed, named reconfigurable dynamics (Re-Dyn). The resulting designs have not only the kinematic properties reconfigurable, such as link lengths, but also properties that directly affect the forces and accelerations, such as masses and inertias. A 2-degree of freedom (DOF) parallel robot is used as a test subject. It is analyzed and redesigned with Re-Dyn. This work also presents the robots forward dynamic model in detail, which includes the force balancing mediums. The connection method is directly utilized for this derivation, which is well suited for multibody dynamics and provides insight for design parameters (DPs). Dynamic performance indices are also briefly discussed as related to the Re-Dyn method. After redesigning the robot, a full simulation is conducted to compare performances related to a flexible manufacturing situation. This illustrates the advantages of the proposed method.

Modular design and development methodology for robotic multi-axis F/M sensors.

Accurate Force/Moment (F/M) measurements are required in many applications, and multi-axis F/M sensors have been utilized a wide variety of robotic systems since 1970s. A multi-axis F/M sensor is capable of measuring multiple components of force terms along x-, y-, z-axis (Fx, Fy, Fz), and the moments terms about x-, y- and z-axis (Mx, My and Mz) simultaneously. In this manuscript, we describe experimental and theoretical approaches for using modular Elastic Elements (EE) to efficiently achieve multi-axis, high-performance F/M sensors. Specifically, the proposed approach employs combinations of simple modular elements (e.g. lamella and diaphragm) in monolithic constructions to develop various multi-axis F/M sensors. Models of multi-axis F/M sensors are established, and the experimental results indicate that the new approach could be widely used for development of multi-axis F/M sensors for many other different applications.

Optimal Trajectory Tracking Control With a 5R Parallel Robot

This work examines the control characteristics of a 5R parallel robotic manipulator subjected to two control studies. Firstly, fundamental aspects of dynamics are presented. Then a brief review of Particle Swarm Optimization (PSO) and feedforward Neural Networks (NN) is undertaken. Subsequently, to tackle the challenging problem of controller parameter tuning for parallel robots in trajectory tracking scenarios, a multi objective optimization problem is formulated for automatic tuning using PSO. This offline method is comparatively evaluated to the Nelder-Mead (NM) sequential simplex optimization scheme. Several results are attained illustrating the strengths and weaknesses of this method for parallel robot control. Then, an adaptive NN model reference control scheme using PSO is proposed. This scheme is proposed as one possible way to take advantage of the strong properties of the PSO online. The scheme is tested and several observations are outlined.Copyright

Experimental study on the control of a novel vibration isolator via adaptive backstepping

This study focuses on the control of a novel active vibration isolator using an adaptive backstepping approach. The developed active isolator is introduced and its dynamic model is presented. It is shown that the unknown nonlinear restoring force and damping parameter pose control challenges. The nonlinear restoring force is approximated as a polynomial with unknown coefficients. Adaptive control is chosen as a suitable approach to tackle the control challenges. An existing lower-order adaptive backstepping controller is modified in order to include the actuator dynamics and avoid the zero convergence of the estimated parameter vector. An extensive experimental study is conducted to test the effectiveness of the modified controller. The performance of the controller is compared with that of the lower-order controller. The results from several testing scenarios are presented and interpreted, and the issues related to parameter estimation and control performance are addressed.

Conceptual design and feasibility study of a novel upper-limb exoskeleton

In recent years, medical devices are becoming more and more important either for rehabilitation or to help people during daily life. For example, upper limb devices are used to recover motor functions after strokes, lesions of the nervous system, traumatic brain injuries or spinal cord injuries. Currently, the most important groups of medical devices for upper limbs are serial exoskeletons and end effector based devices. The existing solutions of these devices are usually fixed onto a structure that releases the patient from the mechanisms weight. This design makes it not possible for the patient to wear the robot during daily life. The purpose of this manuscript is to evaluate the feasibility of a wearable device for the upper limb. This device should not be fixed on a structure, in order to be used during daily life, and not be fixed to a location on the body. In order to accomplish this, a lightweight device is required coupled with good precision. For this reason, a novel parallel exoskeleton has been designed. Because parallel robots suffer from small workspace an innovative solution has been proposed.

Dynamic Performance With Control of a 2DOF Parallel Robot

In this work the dynamic performance and control of a 2DOF parallel robot is conducted. The study is partly motivated by large variations in dynamic performance and control within the reachable workspace of many parallel manipulators. The forward dynamic model of the robot is derived in detail. The connection method is directly utilized for this derivation. Subsequently, a dynamic performance study is undertaken. This reveals important information whilst using a forward dynamic model. A performance index is proposed to determine the variability of performance of the parallel manipulator. Then a trajectory-tracking scenario is undertaken using a linear controller. By means of control, the simulations illustrate the validity of the proposed index for parallel manipulators.Copyright