Gianluca Gatti

Energy harvesting from the vibrations of a passing train: effect of speed variability

This paper builds on a previous study which investigated the amount of energy that could be harvested from the vibration induced by a passing train using a trackside energy harvester. In that study, the optimum parameters of the device were determined for a train passing at a particular speed. However, the effect of the train speed variability on the amount of energy harvested was not explored. In this paper a study is thus undertaken to determine this effect using experimental data from train passages at a site in the UK. Furthermore, a model is developed to investigate the optimum design parameters of the energy harvester when trains pass by at slightly different speeds. This is then validated using the experimental data. It is found that, provided the variability in the train speed is less than about 1% from the nominal speed, then a harvester tuned so that its natural frequency matches one of the trainload dominant frequencies at the line speed is a reasonable design condition.

EXPERIMENTAL VALIDATION OF A SPECIAL LOCKING DRUM BRAKE FOR ROBOTIC APPLICATIONS

The paper presents the development of a novel type of drum brake capable of locking a joint exploiting the effect of self excitation characteristic of this type of brake. A theoretical analysis based on the Reye assumption on wear is first presented, were conditions for self excitement are determined. An initial version of the brake was designed and tested, but it was soon discovered that actuation with solenoids was not appropriate. A second version was then developed where solenoids were replaced by a small motor and reducer placed inside the brake itself, but the resulting drum was too big for the application. Finally a version were the motor and reducer were placed outside the drum was designed. An ad hoc experimental test bed was built using a Maxon motor to control rotation and toque of the drum and to allow an initial wear of the ferodo in order to obtain compliant surfaces. Finally an electronic control of the brakes has been developed.Copyright

Upper and Lower Limbs Rehabilitation: DARTAGNAN, An Alternative Solution to Exoskeletal Robots

This article deals with a new robot for rehabilitation, DARTAGNAN, able to work in active or passive modes, on upper and lower human limbs. The presented robot has an hybrid serial/parallel structure with 6 degree of freedoms and a self-balanced mechanical structure. Although it is not an exoskeleton, DARTAGNAN behaves as such thanks to the customized software and to specific end-effectors, which can be appropriately connected to the forearm or lower leg. Thanks to the force/torque sensor the robot is able to treat the patient limb allowing him/her to (i) feel no effort in passive following mode, (ii) feel a specific effort in passive resistive mode or (iii) to actuate directly the limb in case of force deficit or spasticity for the active mode, while performing the exercise. Moreover, one of features of the robot is the possibility to directly calculate the limbs anthropometric parameters without the need of manual measurements to be set up before each treatment.

Interactive design of patient-oriented video-games for rehabilitation: concept and application

Abstract Purpose: Serious video-games are innovative tools used to train the motor skills of subjects affected by neurological disorders. They are often developed to train a specific type of patients and the rules of the game are standardly defined. A system that allows the therapist to design highly patient-oriented video-games, without specific informatics skills, is proposed. Method: The system consists of one personal computer, two screens, a Kinect™ sensor and a specific software developed here for the design of the video-games. It was tested with the collaboration of three therapists and six patients, and two questionnaires were filled in by each patient to evaluate the appreciation of the rehabilitative sessions. Results: The therapists learned easily how to use the system, and no serious difficulties were encountered by the patients. The questionnaires showed an overall good satisfaction by the patients and highlighted the key-role of the therapist in involving the patients during the rehabilitative session. Conclusions: It was found that the proposed system is effective for developing patient-oriented video-games for rehabilitation. The two main advantages are that the therapist is allowed to (i) develop personalized video-games without informatics skills and (ii) adapt the game settings to patients affected by different pathologies. Implications for rehabilitation Virtual reality and serious video games offer the opportunity to transform the traditional therapy into a more pleasant experience, allowing patients to train their motor and cognitive skills. Both the therapists and the patients should be involved in the development of rehabilitative solutions to be highly patient-oriented. A system for the design of rehabilitative games by the therapist is described and the feedback of three therapists and six patients is reported.

Conceptual design and implantation of an external fixator with improved mobility for knee rehabilitation

Abstract A hinged external fixator is used to allow early knee rehabilitation in case of injury or trauma, as an alternative approach to immobilization. It is mainly adopted for the treatment of dislocations, which involve tearing of the ligaments, and it basically consists of two links connected to each other by a revolute joint. Each link is fixed to the femur and tibia via pin fixation, and the revolute joint is approximately aligned to the knee flexion-extension (FE) axis. The advantage in its implantation is to protect ligament reconstruction, while allowing for an aggressive rehabilitation. Traditional fixators only accommodate the functional flexion movement in a limited range, i.e. where the anatomical movement is closer to a planar circular trajectory. This paper presents the conceptual design and implantation procedure of a double-axis fixator, which accommodates both FE and longitudinal internal-external rotation. The procedure is based on accurate knee kinematics measurements and on computer-aided multibody simulations to assist clinicians in the implantation. An experimental test is presented using an artificial knee, and guidelines are given for in vitro studies. The proposed technique may allow for a better understanding of knee kinematics and have the potential advantage to increase the range of motion in postoperative rehabilitation.

Kinect V2 for Upper Limb Rehabilitation Applications

Many systems have been developed to facilitate upper limb rehabilitation procedures in human subjects affected by trauma or pathologies and to retrieve information about patient performance. The Microsoft Kinect sensor can be used in this context to track body motion and detect objects. In order to evaluate the usability of this device in the upper limb rehabilitation field, a comparison with a marker-based system is presented in this paper. The upper limb motion is specifically considered and the performance on its detection and tracking is evaluated. The effect of the relative location between the Kinect and the observed subject is also investigated through experimental tests performed in different configurations.

An Investigation into the Dynamic Interaction Between an Electro-dynamic Shaker and a Test Structure with Cubic Nonlinearity

This chapter describes the dynamic behaviour of a coupled system where a nonlinear oscillator is attached and driven harmonically by an electro-dynamic shaker. The shaker is modelled as a linear single degree-of-freedom oscillator and the nonlinear attachment is modelled as a hardening Duffing oscillator. The attachment consists of four elastic wires, represented as springs, and its nonlinearity is due to the geometric configuration of the springs, which incline as they extend. The mass of the nonlinear system is much less than the moving mass of the shaker so that the nonlinear system has little effect on the shaker dynamics. The objective is to explore the dynamic behaviour of this system under a range of different conditions. Of particular interest is the situation when the linear natural frequency of the nonlinear system is less than the natural frequency of the shaker such that the frequency response curve of the nonlinear system bends to higher frequencies and thus interacts with the resonance frequency of the shaker. It is found that for some values of the system parameters a two-part frequency response curve can occur: a closed detached curve can appear as a part of the overall amplitude-frequency response, and this detached curve can lie outside or inside the main continuous resonance curve.

Kinematic analysis of an adjustable slider-crank mechanism

In this paper a kinematic analysis of an adjustable slider-crank mechanism is presented. The proposed mechanism is formed by an output member, i.e. the slider, by a connecting rod and by an equivalent crank mechanism, consisting of a pair of identical gears and a connecting link assembled in a typical epicyclical configuration. One point of the planet gear moves along an epicycloidal path, while the other gear is held stationary and the planet arm rotates around a fixed hinge. Such epicycloidal motion is converted into a reciprocating motion of the slider by means of the connecting rod, as in a traditional slider-crank mechanism. By holding the planet arm stationary and modifying the relative angular position of the two gears, an adjustment of the entire mechanism is achieved, in such a way that, if the arm is allowed to rotate again, the slider starts moving according to a different law of motion.