The effect of silicon-carbide fine particle bombardment (FPB) was examined as an easy way to improve the adhesion of diamond-like carbon (DLC) films to a substrate. DLC films were deposited on FPB-treated substrates by plasma-based ion implantation and deposition (PBIID) using CH₄ and C₂H₂ as reactant gases. The adhesion force between the film and substrate was evaluated using the critical load as determined by scratch testing. The FPB treatment improved the adhesion about five times and clearly reduced the wear area of the films. Investigation of the reasons for its effectiveness showed that increased surface roughness accounted for about 67% of the improvement, that increased residual stress of the substrate accounted for about 23%, and that an increased ratio of embedded silicon accounted for about 10%.

View full abstract

This paper deals with the effects of mechanical factors on the filtration speed of a charge injection type of electrostatic oil filter. The new filter has been proposed by Yanada and his coworkers and it has been demonstrated that the filtration speed can be increased to a great or some degree by injecting charges into oils, but the experimental condition was limited. In this paper, the effects of the number of the projections, the electrode spacing, the applied voltage and the oil temperature on the filtration speed are examined using a simple filter model and various types of oil. In order to discuss the effects of those mechanical factors on the filtration speed, numerical simulation of electrostatic field between electrodes is done and the oil flow caused between the electrodes due to ion drag phenomenon, called the ion drag flow in the paper, is observed using a charge coupled devise (CCD) camera and is analyzed using a particle image velocimetry (PIV) technique. The experiments and numerical simulation make clear the effects of the mechanical factors on the filtration speed. An optimal electrode configuration and operating condition are found out.

View full abstract

This paper investigates a human body posture estimation method based on the back projection of human silhouette images extracted from multi-camera images. The multi-camera system is based on a server-client system with local network of 1000Base-T to achieve a voxel 3D reconstruction of human body posture in real-time. In order to extract significant points of the human body such as head, neck, shoulders, elbow joints, hands, waist, knee joints, and toes in 3D, an articulated cylindrical human model is applied to the voxel reconstruction of human body. To evaluate the proposed human body posture estimation method, 3D reconstruction experiments of human body posture and extraction experiments of human body's significant points are carried out. The system runs in approximately real time (9 frames/sec with 50×50×50 voxel resolution) and the experimental results confirm both the feasibility and effectiveness of the proposed system in 3D human body posture estimation.

View full abstract

We discuss a kinematic design of a 3-5R translational parallel mechanism with a large utility workspace. The utility workspace is a closed area, in which the mechanism can move to point without suffering from singularities or running into workspace boundaries. An algorithm for computing the volume of the utility workspace is proposed. We discuss the utility workspace of 3-5R translational parallel mechanisms having three types of chain in consideration of their actuation and constraint singularities. We obtained a 3-RUU translational parallel mechanism with a large utility workspace.

View full abstract

This paper describes the motion control of hyper redundant robots using a learning control scheme based on linear combination of error history. The learning control scheme is formulated with three elements: general solution of inverse kinematics with pseudo inverse of Jacobian matrix to achieve main task, condition to achieve several subtasks and compensation by linear combination of obtained time history of output error. In order to make planar serial manipulator with hyper redundancy achieving main task, tracking of desired trajectory by its output link while performing obstacle avoidance as subtask, several subtask setting schemes to prevent from partially singular configuration caused by interference between main task and subtasks are proposed. The backward learning scheme is also proposed to obtain optimum initial configuration for the proposed learning control scheme. Several simulations and experiments with a planar 10R serial manipulator demonstrate the effectiveness of proposed control scheme.

View full abstract

This paper describes a new method to utilize redundancy of hyper redundant robots. In order to establish the effectively use of enormous amount of redundancy, both of the all actuators' contribution for the achievement of the target motions and capability for unpredictable target motions in future should be maximized simultaneously. From this point of view, two redundancy utilization strategies are proposed based on the different evaluation indices, the movability index of each joint and the assistability index for target motions. These indices are formulated based on the evaluation of angular distribution of the column vectors of Jacobian matrices on velocity of each joint, including the end-effector. Then joint input are derived based on the improved gradient projection method to optimize the indices simultaneously. Motion control simulations and experiments with a planar 10R serial manipulator demonstrated the effectiveness of the proposed method.

View full abstract

MQL is applied to the helical feed milling hole-making process of aluminum alloy. It is difficult to drill on aluminum alloy without cutting fluid because the adhesion to the tool leads to a chip jam, the tool breakage or low accuracy. By employing the helical feed milling, cutting temperature will decrease, each chip length will become short and a chip jam in a hole will be avoided, because the intermittent cutting is realized. As a result of employing the helical feed milling with MQL, it was shown that the shape error is decreased, a burr formation is decreased, machining temperature becomes low and the cutting force becomes small comparing with drilling process. Shape error by helical feed milling with MQL is comparable with that with flood coolant. In this case, small mist particle counts under 5μm, which affects working environment, are almost constant if the spindle speed varies. Scattered mist particle counts are less when MQL is employed over 20000 min-1 spindle speed comparing with the flood coolant.

View full abstract

The fixed-abrasive process has been attracting attention as an alternative to the abrasive-free process for finishing surfaces, by virtue of its capacity to improve formability and alleviate environmental problems. Here, we focus on a super-finishing method that uses fine diamond stones. Super-finishing was attempted using low-pressures (< 0.5 MPa) with diamond abrasives averaging less than 3 μm in diameter. We investigated the influence of super-finishing parameters on the surface finish under low-pressure conditions for borosilicate glass. The following conclusions were reached. (1) The surface finish decreased with decreasing stone pressure for ductile cutting. By using a stone pressure of 0.1 MPa, a surface finish of 2 nm R_a with the #12,000 grindstone (mean grain diameter of 0.25 μm) was obtained. (2) Decreasing the mean grain diameter of the abrasive grains decreased the surface finish and could reduce crack formation. (3) A finer surface finish was obtained by increasing the volumetric grain percentage of the grindstone. (4) The maximum crossing angle minimally influenced the surface finish under low-pressure conditions. (5) We found the parameter groove aspect ratio and a method to reduce swell-out height. (6) We successfully demonstrated an evaluation method for polished surfaces and the cutting types. (7) Cracks are reduced on finished surfaces by keeping the depth of cut to less than 100 nm in the case of borosilicate glass.

View full abstract

Two methods to solve a conforming contact problem are proposed. First method is general and can be applicable to the contact case between elastic arbitrary shape bodies. For verification FEA is performed on the convex-concave sphere contact, and the result of this method is well corresponding to the FEA result. However, the accuracy deteriorates when the mesh aspect ratio is extremely large. This phenomenon is caused by the usage of numerical integration for the calculation of influence coefficient. The second method is devised to avoid this problem, while this improved method is applicable only to the case when the contact area can be considered to be on a cylinder surface. By using this method, the contact pressure can be obtained without the deterioration even in the case of edge load occurring between ball bearing race shoulder and ball. The results of the contact pressure and the shear stress that is necessary for bearing life estimation are compared with the FEA result, which showed well correspondence.

View full abstract

The exoskeleton robot is worn by the human operator as an orthotic device. Its joints and links correspond to those of the human body. The same system operated in different modes can be used for different fundamental applications; a human-amplifier, haptic interface, rehabilitation device and assistive device sharing a portion of the external load with the operator. We have been developing exoskeleton robots for assisting the motion of physically weak individuals such as elderly or slightly disabled in daily life. In this paper, we propose a three degree of freedom (3DOF) exoskeleton robot (W-EXOS) for the forearm pronation/ supination motion, wrist flexion/extension motion and ulnar/radial deviation. The paper describes the wrist anatomy toward the development of the exoskeleton robot, the hardware design of the exoskeleton robot and EMG-based control method. The skin surface electromyographic (EMG) signals of muscles in forearm of the exoskeletons' user and the hand force/forearm torque are used as input information for the controller. By applying the skin surface EMG signals as main input signals to the controller, automatic control of the robot can be realized without manipulating any other equipment. Fuzzy control method has been applied to realize the natural and flexible motion assist. Experiments have been performed to evaluate the proposed exoskeleton robot and its control method.

View full abstract