This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluids (MRF), magnetorheological elastomers (MRE) and magnetorheological plastomers (MRP). To easily understand the history of sensing research using these two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensors, tactile devices, strain sensors, wearable bending sensors, magnetometers, display devices and flux measurement sensors. After briefly describing what has been reviewed in a conclusion, several challenging future works, which should be undertaken for the practical applications of sensors or/and sensing devices, are discussed in terms of response time and new technologies integrating with artificial intelligence neural networks in which several parameters affecting the sensor signals can be precisely and optimally tuned. It is sure that this review article is very helpful to potential readers who are interested in creative sensors using not only the proposed smart materials but also different types of smart materials such as shape memory alloys and active polymers.

This study explores the significance of active suspension systems for vehicles with lower chassis compared to conventional ones, aiming at the development of future automobiles. Conventional linear MR (magnetorheological) dampers were found inadequate in ensuring sufficient vibration control because the vehicle’s chassis becomes lowered in the unmanned vehicles or purposed-based vehicles. As an alternative, a rotary type of MR damper is proposed in this work. The proposed damper is designed based on prespecified design parameters through mathematical modeling and magnetic field analyses. Subsequently, a prototype of the rotary MR damper identical to the design is fabricated, and effectiveness is shown through experimental investigations. In configuring the experiments, a proportional-integral (PI) controller is employed for current control to reduce the response time of the damper. The results presented in this work provide useful guidelines to develop a new type of MR damper applicable to various types of future vehicles’ suspension systems with low distance from the tire to the body floor.

This paper proposes a new type of tactile transfer cell which can be effectively applied to robot-assisted minimally invasive surgery (RMIS). The proposed tactile device is manufactured from two smart materials, a magnetorheological fluid (MRF) and a magnetorheological elastomer (MRE), whose viscoelastic properties are controllable by an external magnetic field. Thus, it can produce field-dependent repulsive forces which are equivalent to several human organs (or tissues) such as a heart. As a first step, an appropriate tactile sample is made using both MRF and MRE associated with porous foam. Then, the microstructures of these materials taken from Scanning Electron Microscope (SEM) images are presented, showing the particle distribution with and without the magnetic field. Subsequently, the field-dependent repulsive force of the sample, which is equivalent to the stress relaxation property of viscoelastic materials, are measured at several compressive deformation depths. Then, the measured values are compared with the calculated values obtained from Young’s modulus of human tissue data via the finite element method. It is identified from this comparison that the proposed tactile transfer cell can mimic the repulsive force (or hardness) of several human organs. This directly indicates that the proposed MR materials-based tactile transfer cell (MRTTC in short) can be effectively applied to RMIS in which the surgeon can feel the strength or softness of the human organ by just changing the magnetic field intensity. In this work, to reflect a more practical feasibility, a psychophysical test is also carried out using 20 volunteers, and the results are analyzed, presenting the standard deviation.

This paper proposes a cylindrical grip type of tactile device that is effectively integrated to a surgical robot console so that a surgeon can easily touch and feel the same stiffness as the operating organs. This is possible since the yield stress (or stiffness) of magnetic-responsive materials can be tuned or controlled by the magnetic field intensity. The proposed tactile device consists of two main parts: a magnetorheological elastomer (MRE) layer and a magnetorheological fluid (MRF) core. The grip shape of the device to be positioned on the handle part of the master of the surgical robot is configured and its operating principle is discussed. Then, a couple of equations to calculate the stiffness from the gripping force and the field-dependent yield stress of MRF are derived and integrated using the finite element analysis (FEA) model. After simulating the stiffness of the proposed tactile device as a function of the magnetic field intensity (or current), the stiffnesses of various human organs, including the liver and heart, are calculated from known data of an elastic modulus. It is demonstrated from comparative data between calculated stiffness from human tissues and simulated stiffness from FEA that the proposed tactile device can generate sufficient stiffness with a low current level to recognize various human organs which are significantly required in the surgical robot system.

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli, an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluid (MRF), magnetorheological elastomer (MRE) and magnetorheological plastomer (MRP). To easily understand the history of sensing research using the two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss on the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensor, tactile device, strain sensor, wearable bending sensor, magnetometer, display device and flux measurement sensor. After briefly describing what have been reviewed in a conclusion, several challenging future works, which should be done for practical applications as sensors or sensing devices, are remarked in terms of new technologies such as artificial intelligence neural network in which several parameters affecting the sensor signals can be precisely tuned or controlled. It is sure that this review article is very helpful to make creative sensors using not only the proposed smart materials but also several different types of smart materials including shape memory alloys and active polymers.

This work investigates the effect of spool displacement control of the piezoelectric stack actuator (PSA) based valve system on the flow motion of the pressure drop and flow rate. As a first step, the governing equations of the structural parts of the displacement amplifier and spool are derived, followed by the governing equation of the fluid part considering control volume and steady flow force. Then, an appropriate size of the valve is designed and manufactured. An experimental apparatus to control the spool displacement is set up in the heat chamber and tracking control for the spool displacement is evaluated at 20 °C and 100 °C by implementing a proportional-integral-derivative (PID) feedback controller. The tracking controls of the spool displacement associated with the sinusoidal and triangular trajectories are realized at 20 °C and 100 °C. It is demonstrated that the tracking controls for the sinusoidal and triangular trajectories have been well carried out showing the tracking error less than 3 μm at both temperatures. In addition, the flow motions for the pressure drop and the flow rate of the proposed valve system are experimentally investigated. It is identified from this investigation that both pressure drop and flow rate evaluated 20 °C have been decreased up to 18% at 100 °C. This result directly indicates that the temperature effect to control performance of the structural part and fluid part in the proposed PSA based valve system is different and hence careful attention is required to achieve the successful development of advanced valve systems subjected to a wide range of the operating temperature.