Inductively-coupled wireless power transfer (IWPT) is promising to power a freely moving capsule robot (CR) continuously. Existing IWPT system for this application normally adopts a single-layer Helmholtz coil (SHC), which can generate a uniform alternating magnetic field (AMF) to cover the CR workspace, but leads to a low power transfer efficiency (PTE). To improve the PTE, this paper proposes a novel double-layer Helmholtz coil (DHC). The DHC is composed of two in-parallel connected SHCs that have identical coil turns and winding directions but different diameters. To design and optimize the DHC, a dedicated analytical model, is built and verified. A comparison between the DHC and SHC is also conducted, which shows that the DHC can not only generate a uniform AMF to cover a larger region, but its power consumption is lower when the generated AMF is identical, thus improving the PTE. Finally, the DHC is used to power a three-dimensional receiving coil, and the achieved PTE is in a range of 7.58%∼17.41%, higher than that when using the SHC, which is in a range of 6.74%∼14.92%.

Wireless power transmission (WPT) for a capsule robot (CR) has always been a challenging issue because the unpredictable CR attitude can destabilize the induced power of the receiving coil onboard the CR. This article proposes a new WPT system for stably powering the CR, and it mainly consists of a rotatable two-dimensional transmitting coil (R2DTC), a one-dimensional receiving coil (1DRC), and an attitude detection module (ADM). The R2DTC can excite a uniform and directional alternating magnetic field (AMF) covering the CR workspace, and the AMF amplitude and direction are controllable in the 3-D space. The 1DRC has a shape of thin-walled ring, for ease of being used as a CR outer shell. The ADM is fixed together with the 1DRC; it can detect the 1DRC attitude in real time and is implemented in a compact size. Referring to the 1DRC attitude, the R2DTC can regulate the AMF to stabilize the 1DRC induced power. This article presents design and implementation details of the WPT system, as well as experiments for its performance evaluation. The R2DTC is verified to supply stable power of 500 mW to the attitude-changing 1DRC at most cases, with a transfer efficiency ranging from 8.15% to 13.53%.

Wireless power transfer (WPT) technology has been widely researched and developed, especially the omnidirectional WPT system. Despite much attention, the omnidirectional WPT system generating 3-D magnetic field is rarely reported for capsule robot (CR) applications. In this article, we propose a genuine omnidirectional system for CR using only one pair of power transmitting coils (PTCs) and one power receiving coil (PRC) for the first time. The novel PTC with a compact and compatible structure is capable of generating 3-D magnetic field at any position. In particular, a single power source is solely utilized to drive the PTC without current amplitude or phase control methods. Based on the magnetic calculation and finite-element simulation, the geometric parameters of the proposed PTC structure are determined. Additionally, through the theoretical analysis and comparison with traditional topology, the capability of omnidirectional transfer can be verified. Furthermore, in order to dynamically adjust the PTC rotation, the corresponding received voltage tracking-based control strategy is also illustrated. Finally, a practical prototype is built, and experimental results confirm the omnidirectional WPT capability of the proposed system concerning both positions and attitudes, as well as the effectiveness of the control method. It demonstrates a maximum power delivered to the load of 2523 mW with a power transfer efficiency of 8.4%.

A non-invasive method for gastrointestinal parameter monitoring

This paper proposes a new prototype of wireless micro-robot system for endoscope. The micro-robot we have fabricated and tested is able to propel itself in the intestine canal of pig in an autonomous manner by earthworm locomotion. It is different from the conventional micro-robot endoscope that wireless module is used for communicating and power transfer being up to 480 mW of DC power for receiving coil in the proposed system. The system composes of wireless communications module, personal computer, micro-robot, wireless power transfer controller and wireless power transfer coil. The experimental results show that the driving voltage of micro-robot is stable which fulfils the need of the micro-robot system. The micro-robot can creep reliably in the rubber canal and the intestinal canal of pig.

This paper presents the design of a wireless capsule system for monitoring the physiological signals of the human gastrointestinal (GI) tract. The primary components of the system include a wireless capsule, a portable data recorder, and a workstation. Temperature, pH, and pressure sensors; an RF transceiver; a controlling and processing application specific integrated circuit (ASIC); and batteries were applied in a wireless capsule. Decreasing capsule size, improving sensor precision, and reducing power needs were the primary challenges; these were resolved by employing micro sensors, optimized architecture, and an ASIC design that include power management, clock management, a programmable gain amplifier (PGA), an A/D converter (ADC), and a serial peripheral interface (SPI) communication unit. The ASIC has been fabricated in 0.18- μm CMOS technology with a die area of 5.0 mm × 5.0 mm. The wireless capsule integrating the ASIC controller measures Φ 11 mm × 26 mm. A data recorder and a workstation were developed, and 20 cases of human experiments were conducted in hospitals. Preprocessing in the workstation can significantly improve the quality of the data, and 76 original features were determined by mathematical statistics. Based on the 13 optimal features achieved in the evaluation of the features, the clustering algorithm can identify the patients who lack GI motility with a recognition rate reaching 83.3%.