Mihai Dupac

This paper aims to investigate the performance of a hydraulic actuator controlled by the novel system microindependent metering (MIM). This analysis has been performed by comparing the models of two systems which are the traditional independent metering (IM), which depends on poppet valve, and the new hydro‐mechatronics system MIM, which relies on a stepped rotary flow control valve. In general, IM is a hydraulic control system which guarantees a separation between the meter‐in and the meter‐out of the hydraulic actuator. A Valvistor valve, a special type of Poppet valves, was developed to be embedded into the IM system. This valve has controllability and stability shortcomings which prevent the system from spreading in the industrial applications. The Valvistor valve performance is highly affected by the fluid disturbances because the fluid is considered as a part of its control elements. A stepped rotary flow control valve has been developed to control hydraulic flow rate. The valve composed of a rotary orifice attached to a stepper motor. Using this valve instead of the traditional poppet type has led to a new configuration, which is termed by MIM. This form improves the hydraulic cylinder velocity performance by rejecting the fluid disturbances effect on the control circuit.

In this paper a newly 3D path planning approach and curve generation for design and manufacturing efficiency is considered. The 3D path is generated by a combination of piecewise interpolating curves - along a given number of via-points - created via a spherical coordinate system specified by the polar angles, radial distances and the associated azimuthal angles. Each piecewise interpolating curve is constructed using Hermite polar interpolation in the projective polar plane and the rotating azimuthal plane. To verify the proposed approach, numerical simulations for the generation of a helix design, a 4 and 6 leaf design and a trajectory planning of a picking robot arm are conducted.

In this paper a combined polar‐Cartesian approach to generate a smooth trajectory of a robotic arm along priori defined via‐points is presented. Due to the characteristics/geometry of the robotic arm, cylindrical coordinates are associated with the trajectory of motion. Possible trajectories representing the system dynamics are generated by mix matching higher order polar piecewise polynomials used to devise the radial trajectory and Cartesian piecewise polynomials used to calculate the related height in a normal plane unfolded along the radial trajectory of the motion. To describe the kinematic properties of the end‐effector a moving non‐inertial orthonormal Frenet frame is considered. Using the Frenet frame, the components of the velocity and acceleration along the frame unit vectors are calculated. Numerical simulations are performed for two different configurations in order to validate the approach.

In this paper, the mathematical modeling and trajectory planning of a 3D rotating manipulator composed of a rotating‐prismatic joint and multiple rigid links is considered. Possible trajectories of the end effector of the manipulator—following a sequence of 3D target points under the action of 2 external driving torques and an axial force—are modeled using zenithal gnomic projections and polar piecewise interpolants expressed as polynomial Hermite‐type functions. Because of the geometry of the manipulator, the time‐dependent generalized coordinates are associated with the spherical coordinates named the radial distance related to the manipulator length, and the polar and azimuthal angles describing the left and right and, respectively, up and down motion of the manipulator. The polar trajectories (left and right motion) of the end effector are generated using a inverse geometric transformation applied to the polar piecewise interpolants that approximate the gnomic projective trajectory of the 3D via‐points. The gnomic via‐points—located on a projective plane situated on the northern hemisphere—are seen from the manipulator base location, which represents the center of rotation of the extensible manipulator. The related azimuthal trajectory (up and down motion) is generated by polar piecewise interpolants on the azimuthal angles. Smoothness of the polygonal trajectory is obtained through the use of piecewise interpolants with continuous derivatives, while the kinematics and dynamics implementation of the model is well suited to computer implementation (easy calculation of kinematics variables) and simulation. To verify the approach and validate the model, a numerical example—implemented in Matlab—is presented, and the results are discussed.

Traditional shoulder range of movement (ROM) measurement tools suffer from inaccuracy or from long experimental setup times. Recently, it has been demonstrated that relatively low-cost wearable inertial measurement unit (IMU) sensors can overcome many of the limitations of traditional motion tracking systems. The aim of this study is to develop and evaluate a single IMU combined with an electromyography (EMG) sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity across the shoulder ROM. Six volunteer subjects with healthy shoulders and one participant with a ‘frozen’ shoulder were recruited to the study. Arm movement in 3D space was plotted in spherical coordinates while the relative EMG intensity of any arm position is presented graphically. The results showed that there was an average ROM surface area of 27291 ± 538 deg² among all six healthy individuals and a ROM surface area of 13571 ± 308 deg² for the subject with frozen shoulder. All three sections of the deltoid show greater EMG activity at higher elevation angles. Using such tools enables individuals, surgeons and physiotherapists to measure the maximum envelope of motion in conjunction with muscle activity in order to provide an objective assessment of shoulder performance in the voluntary 3D workspace.

In this paper the validation of a rig capable of simulating the dynamic response of an energy storing and returning composite prosthetic foot during amputee running is considered. It is shown that the rig can simulate the running action of an amputee runner and return similar ground contact time. It has also been shown that if a small input force is applied in a timed and sympathetic manner to the prosthetic spring-mass system the amplitude of oscillation increases which agrees with results of previous research. The rig will allow the design variables that contribute to the response of a prosthetic foot during running to be understood and optimised to possible improve the foot's performance.

In this paper the design of a rig capable to simulate the dynamic response of an energy storing and returning composite prosthetic foot during amputee running is considered. It has been assumed that the amputee/prosthesis system can be modelled as a spring/mass system. Therefore the rig has been designed to allow the applied mass, input force and foot contact point of various feet designs to be varied to test this assumption. The rig will allow the design variables that contribute to the response of a prosthetic foot during running to be understood and optimised to improve the foot's performance.