This paper introduces a novel micro-domain force estimation method for applications in a magnetic-haptic micromanipulation platform (MHMP). The MHMP employs the magnetic levitation technology in micro-domain worlds for ultra-high precision micromanipulation. In the MHMP, a microrobot that consists of a magnetic head and a body that includes electronic parts and an end-effector is manipulated by regulating an external magnetic field. The MHMP has been equipped with a haptic technology to allow a human operator to feel micro-domain environments and to intervene in dexterous tasks due to the poor knowledge from micro-worlds. To preserve a high feeling of a micro-domain environment for a human operator, the applied force/torque from the environment to the microrobot are required to be directly measured by specific sensors. Due to the size restriction, attaching force sensors to our microrobot is impractical. Therefore, we use a combination of Hall-effect sensor in the structure of the MHMP to estimate a single-axis force, eliminating the need for sensors on the microrobot. The Hall-sensors measure the magnetic flux and determine the location of the horizontally zero magnetic field gradient, Bmax location. It was realized that the applied force from the environment to the microrobot is linearly proportional to the distance of the microrobot from the Bmax location. The magnetic force which is equal to the environment force is calibrated using a cantilever deflection. The developed micro-domain force estimation method is verified experimentally, and it was demonstrated that this method has promising potential in estimating the environmental force applied to the microrobot in a non-contact way.
Precise processes or devices utilizing scanning nanoprobes, e.g., probe-based nanolithography and probe-based data storage, are state-of-the-art technologies that can handle nm-sized tiny patterns. To transfer these technologies from the research and development stage to practical implementation, a significant improvement in the wear resistance of the probe tip is required for reliable and long-term operation of the system. On the other hand, to remove the unevenness of the size of drawn patterns or recorded bits, the electric contact resistance at the nanoscale sliding contact area of the probe tip must be stable even when the scanning speed of the probe increases to achieve higher throughput. To solve these dilemmatic problems, tribological investigation of the probe tip is very important. In this study, the influence of the material properties on the relations among electric contact resistance, friction force, and wear durability of nanoprobe tips was examined in detail to clarify the tribological phenomena that occur at the nanoscale contact area of the probe tips. From the results, the authors discussed the key material properties that are dominant for the abovementioned three tribological factors. In conclusion, management of the surface oxide thickness of metal electrodes was the key among all the three factors.
The galvanometer scanner is a type of swaying motor used in laser-drilling machines that is able to position the laser at more than 2,000 points per second. In recent years, the number of holes in printed circuit boards for mobile phones and other electronic devices has increased, so printed circuit boards now have layers and high-density patterns. Therefore, most of the motions of galvanometer scanners are for a short distance and time. The balls in the bearings do not go into 360° rolls, so fretting damage occurs over a long period of time. This is likely to have an adverse effect on positioning accuracy. In this paper, we propose a deterioration diagnosis method for galvanometer scanners that focuses on ball bearing wear. The proposed method can be used to determine the extent of damage and if the ball bearings need to be replaced. The effectiveness of the proposed method was verified by experiments using galvanometer scanners with laser drilling machines over a long period of time.
This paper presents an adaptive feed-forward cancellation (AFC) technique with a damping function based on optimized AFC. The proposed AFC includes a mechanical resonance characteristic as an internal model that is realized by using the damping function and that achieves the best performance in the frequency domain. This makes it possible to apply the proposed AFC to suppress not only repeatable run-out (RRO) but also non-repeatable run-out (NRRO) of the head positioning system in hard disk drives. Simulation results showed that the proposed AFC can suppress NRRO such as disk flutter vibration and that the stability of the feedback loop was improved by the damping function.
The purpose of this study was to investigate vibrations suppression control methods of image transfer belt system which is widely applied in image formation procedure of printers and copy machines. The study focused on vibrations caused by loading torque of printing mediums when they were delivered into the machinery. The system was modelled as a four-rollers-belt with a stepper motor based on exist apparatus. Equations of motion and vibration of the four-rollers-belt system were established. Two types of description about the vibrations in the image forming part of belt, stretching displacement and absolute displacement were defined and selected as main inhibited quantities. Impacts on the two quantities by several parameters of the system, including Young's modulus of belt, rotational stiffness of motor coupling were studied. Additional flywheels and dynamic absorbers were used to improve the system performance, and an evaluation function was defined to estimate the effects. The results indicated that the two devices reduced the two displacements, and the outcomes varied as different attached locations and moment of inertia. It confirmed that by adding a flywheel with large inertia on burden roller, or a dynamic vibration absorber on drive roller could achieve better suppression results.
An urgent need exists to predict the stress of a piping system connected to scroll compressors. Predicting the stress of a piping system is a useful way to help reduce the cost of developing products consisting of a piping system and scroll compressors. To meet this need, we investigated two main factors used to predict piping stress: the excitation forces of the scroll compressors and the vibration response of the piping system. We calculated the excitation forces and validated the results experimentally and calculated the vibration response by using the excitation forces and a finite-element model of the piping system. The calculated stress values agreed well with experimentally measured ones.
In recent years, many myoelectric arms that are controlled based on electromyogram (EMG) signals of amputee's stump or residual muscles have been proposed. In the cases of above elbow amputees, however, the muscles which generate the forearm, wrist and hand motions do not remain. Therefore, most myoelectric arms for above elbow amputees have less degree of freedom and its dexterity is relatively poor compared with a human upper-limb. To improve the quality of life of above elbow amputees and to increase their mobility in daily life activities, some additional input signals must be prepared. One of the strong candidates of the additional input signals is an electroencephalogram (EEG) signal. An EEG signal is an electric signal that can be measured along a scalp, so that it can be measured even with an above elbow amputee. In this study, an artificial arm for above elbow amputees is controlled based on EMG and EEG signals. In this paper, the EEG-based motion estimation method is proposed to control the forearm supination/pronation motion of the artificial arm. The angle, angular velocity, and angular acceleration of the forearm motion are estimated under several velocities by using EEG signals.
We developed a new whole body motion support type mobile suit. This suit can be used separately for supporting the upper and/or lower limbs, for assisting in ADL (Activities of Daily Living). We also developed a mobile lifter system which can bear both the equipped person and the suit. This suit and the lifter can be used by motor palsy patients, people who have suffered a stroke, spinal-cord-injury patients, and people with central nerve disorders. Using this device, these patients can recover normal gait with no risk of falling. In this paper, the cerebral activity during walking using the suit and normal gait without the suit are compared. According to multiple trials with the suit on a treadmill, the activities of the premotor area sensory motor cortex decreased. Especially, while walking using the suit for supporting lower limbs without swinging arms, the cerebral activities of most of the areas decreased. This data shows that it bcomes ineffective for patients accustomed to the suit in rehabilitation. However, on the contrary, by walking while swinging bilateral arms (even though these arms were assisted by the suit), the activity in the supplementary motor area increased (this area of the brain is related with memory of motion). Furthermore, the cerebral activities while walking on a treadmill and while walking in a corridor with an outside view were compared using NIRS (Near-Infrared Spectroscopy). From the results of this experiment, we found it is most effective for gait training to actually walk and not stay fixed in one location. We also found it is important for patients to swing their arms during gait training in rehabilitation.