This paper describes a position sensor with six degrees of freedom (DoF) measurement capability. This sensor is designed for the position sensing of the rotor in a bearingless slice motor to enable active control. The sensor is designed to fit entirely under the rotor and operates by accessing the rotor bottom surface only, enabling packaging of the pump on the top of the rotor. The sensor has two parts; both operate using eddy currents. One of these parts measures the two radial DoF of the rotor. The other part measures the axial, angular rotation and tip/tilt DoF. The sensor utilizes a conductive target fixed to the underside of the rotor. Motion of this target varies the magnetic fields which can then be measured by the sensor as variation in either induced voltage or inductance value. The design and fabrication of the sensor along with the signal processing methods are presented in detail. The radial position measurements are the most critical for active levitation due to the small working gaps in these DoF, hence a resolution of and bandwidth of 1 kHz is achieved. This paper also describes the closed-loop behavior of a bearingless motor using this sensor.

Robotic ultrasonography potentially acts as an essential aid to medical diagnosis. To overcome the limitations in robotic ultrasonography, in this paper, we proposed a novel self-adaptive parallel manipulator (SAPM) that can automatically adjust the ultrasound (US) probe pose to adapt to various contours of scanned areas, provide approximate constant operating forces/torques, achieve mechanical measurement, and cushion undesired produced forces. A novel parallel adjustment mechanism is proposed to attain automatic pose adjustment with 3 degrees of freedom (DOFs). This mechanism enables the US probe to adapt to different scanned areas and to perform the scanning with approximate constant forces and torques. Besides, we present a mechanical measurement and safety protection method that can be integrated into the SAPM and used as operation status monitoring and early warning during scanning procedures by capturing operating forces and torques. Experiments were carried out to calibrate the measurement and buffer units and evaluate the performance of the SAPM. Experimental results show the ability of the SAPM to provide 3-DoFs motion and operating force/torque measurement and automatically adjust the US probe pose to capture US images of equally good quality compared to a manual sonographer scan. Moreover, it has characteristics similar to soft robots that could significantly improve operation safety, and could be extended to some other engineering or medical applications.

We present a new configuration of bearingless slice motor that levitates and rotates a ring-shaped solid steel reluctance rotor. The rotor is 50 mm in diameter and has salient features on the outer surface. Symmetric sets of Halbach magnet arrays, mounted on the tips of stator teeth, establish a homopolar bias flux around the rotor. The bias flux passively stabilizes the rotor in the out-of-plane tilts and axial translation, whereas the rotor's radial translations are actively stabilized by feedback control. The rotor saliencies spatially modulate the air-gap bias flux such that the resulting torque-current relationship is similar to that of permanent-magnet synchronous machines. We have designed, built, and tested a prototype bearingless motor and control system. The prototype system achieves a torque constant of 14.9mNm/A, maximum speed of 5500 rpm, and suspension bandwidth of 84 Hz with a phase margin of 11.3 deg. The rated torque and speed are 26.8 mNm and 3486 rpm, and the axial and tilting passive stiffnesses are 15.3 N/mm and 34.4 mNm/deg.

A threshold signal detector is proposed to improve the state estimation accuracy of an extended Kalman filter (EKF) and is validated experimentally with a MEMS electrostatic micro-scanner. A first order derivative of Gaussian (DOG) filter is used to detect and locate rapid changes in voltage signal caused by crossing of a threshold angle determined by maximum overlap of capacitive electrodes. The event-triggered measurement is used in the update step of the EKF to provide intermittent but more accurate angle measurements than those of the capacitive sensor's continuous output. Experiments on the electrostatic micro-scanner show that with the threshold signal detector incorporated, the average position estimation accuracy of the EKF is improved by 15.1%, with largest improvement (30.3%) seen in low signal-to-noise ratio (SNR) conditions. A parametric study is conducted to examine sampling frequency and capacitance profile, among other factors that may affect detection error and EKF accuracy.

This paper presents the design procedure for a new multi-cycle resonance-based voltage boosting rectifier (MCRR) capable of delivering a desired amount of power to the load (PDL) at a designated high voltage (HV) through a loosely-coupled inductive link. This is achieved by shorting the receiver (Rx) LC-tank for several cycles to harvest and accumulate the wireless energy in the RX inductor before boosting the voltage by breaking the loop and transferring the energy to the load in a quarter cycle. By optimizing the geometries of the transmitter (Tx) and Rx coils and the number of cycles, , for energy harvesting, through an iterative design procedure, the MCRR can achieve the highest PDL under a given set of design constraints. Governing equations in the MCRR operation are derived to identify key specifications and the design guidelines. Using an exemplary set of specs, the optimized MCRR was able to generate 20.9 V across a 100 kΩ load from a 1.8 V, 6.78 MHz sinusoid input in the ISM-band at a Tx/Rx coil separation of 1.3 cm, power transfer efficiency (PTE) of 2.2%, and = 9 cycles. At the same coil distance and loading, coils optimized for a conventional half-wave rectifier (CHWR) were able to reach only 13.6 V from the same source.

A piezoelectric sensor with a floating element was developed for direct measurement of flow induced shear stress. The piezoelectric sensor was designed to detect the pure shear stress while suppressing the effect of normal stress generated from the vortex lift-up by applying opposite poling vectors to the piezoelectric elements. During the calibration stage, the prototyped sensor showed a high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high piezoelectric coefficients ( =-1330 pC/N) of the constituent 0.67Pb(MgNb)O-0.33PbTiO (PMN-33%PT) single crystal. By contrast, the sensor showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the sensing structure. The usable frequency range of the sensor is up to 800 Hz. In subsonic wind tunnel tests, an analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements. For dynamic stress measurements, the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing. The developed piezoelectric shear stress sensor was found to have an SNR of 15.8 ± 2.2 dB and a sensitivity of 56.5 ± 4.6 pC/Pa in the turbulent flow.

Robotic systems have slowly entered the realm of modern medicine; however, outside the operating room, medical robotics has yet to be translated to more routine interventions such as blood sampling or intravenous fluid delivery. In this paper, we present a medical robot that safely and rapidly cannulates peripheral blood vessels-a procedure commonly known as venipuncture. The device uses near-infrared and ultrasound imaging to scan and select suitable injection sites, and a 9-DOF robot to insert the needle into the center of the vessel based on image and force guidance. We first present the system design and visual servoing scheme of the latest generation robot, and then evaluate the performance of the device through workspace simulations and free-space positioning tests. Finally, we perform a series of motion tracking experiments using stereo vision, ultrasound, and force sensing to guide the position and orientation of the needle tip. Positioning experiments indicate sub-millimeter accuracy and repeatability over the operating workspace of the system, while tracking studies demonstrate real-time needle servoing in response to moving targets. Lastly, robotic phantom cannulations demonstrate the use of multiple system states to confirm that the needle has reached the center of the vessel.

This paper presents a new method, called multi-cycle Q-modulation, which can be used in wireless power transmission (WPT) to modulate the quality factor (Q) of the receiver (Rx) coil and dynamically optimize the load impedance to maximize the power transfer efficiency (PTE) in two-coil links. A key advantage of the proposed method is that it can be easily implemented using off-the-shelf components without requiring fast switching at or above the carrier frequency, which is more suitable for integrated circuit design. Moreover, the proposed technique does not need any sophisticated synchronization between the power carrier and Q-modulation switching pulses. The multi-cycle Q-modulation is analyzed theoretically by a lumped circuit model, and verified in simulation and measurement using an off-the-shelf prototype. Automatic resonance tuning (ART) in the Rx, combined with multi-cycle Q-modulation helped maximizing PTE of the inductive link dynamically in the presence of environmental and loading variations, which can otherwise significantly degrade the PTE in multi-coil settings. In the prototype conventional 2-coil link, the proposed method increased the power amplifier (PA) plus inductive link efficiency from 4.8% to 16.5% at ( = 1 kΩ, = 3 cm), and from 23% to 28.2% at ( = 100 Ω, = 3 cm) after 11% change in the resonance capacitance, while delivering 168.1 mW to the load (PDL).

Power transfer efficiency (PTE) and power delivered to the load (PDL) are two key inductive link design parameters that relate to the power source and driver specs, power loss, transmission range, robustness against misalignment, variations in loading, and interference with other devices. Designers need to strike a delicate balance between these two because designing the link to achieve high PTE will degrade the PDL and vice versa. We are proposing a new figure-of-merit (FoM), which can help designers to find out whether a two-, three-, or four-coil link is appropriate for their particular application and guide them through an iterative design procedure to reach optimal coil geometries based on how they weigh the PTE versus PDL for that application. Three design examples at three different power levels have been presented based on the proposed FoM for implantable microelectronic devices, handheld mobile devices, and electric vehicles. The new FoM suggests that the two-coil links are suitable when the coils are strongly coupled, and a large PDL is needed. Three-coil links are the best when the coils are loosely coupled, the coupling distance varies considerably, and large PDL is necessary. Finally, four-coil links are optimal when the PTE is paramount, the coils are loosely coupled, and their relative distance and alignment are stable. Measurement results support the accuracy of the theoretical design procedure and conclusions.