Search results

This paper describes one of the new package cooling technology concepts using low melting point alloys in order to perform high density packaging. Two kinds of cooling alloy materials, Bi/Sn/In and Bi/Pb/Sn/ln, whose melting points were less than 80°C and whose costs were low, were selected. The experimental substrate sample was fabricated by greensheet technology on which a tungsten metallised resistor heater was formed. Two kovar weld rings were brazed together to the top side and back side surfaces of the substrate individually. One kovar metal shell was laser welded to the top side weld ring in order to protect many devices. Another kovar metal shell, with a hole in the centre, was laser welded to the back side weld ring. The low melting point alloy was melted and poured into the back side kovar shell through the hole in a liquid state. After it was cooled and changed into a solid state, the hole was sealed hermetically with a small kovar metal cap by a laser beam. The authors performed a thermal experiment and confirmed that the substrate back surface temperature was fixed at the cooling alloy material's melting point for several minutes by thermal absorption while the low melting point alloy phase changed from its original solid state into a liquid state. This new package cooling technology is extremely useful for a high power motor drive circuit package which consists of many high power transistor chips and other analogue IC chips, and whose motor drive operation is performed intermittently for several minutes with some interval times.

The purpose of this paper is to describe a standing style transfer system, ABLE, designed to enable a person with disabled lower limbs to do daily‐life activities without special infrastructure. Actually, ABLE is mainly intended for use by people who have spinal cord injuries and who cannot move hip joints and lower extremities: the level of spinal cord injury is L1.

ABLE comprises three modules: a powered lower extremity orthosis, a pair of telescopic crutches, and a pair of mobile platforms. When traveling in a standing position, the user wears the powered lower extremity orthosis to fix his posture, and rides on the mobile platforms. The user uses crutches to keep his body stable. These telescopic crutches also play an important role of power assistance in standing‐up and sitting‐down motions, or going up/down a step. The user can enter narrow spaces, although stability is emphasized in wide spaces because it is possible to alter the contact points of the crutches freely.

Motions are discussed in a standing position: traveling and rotating, and the chair and step motions. Experimental results related to these motions confirm the design's effectiveness. The authors improve previously developed mobile platforms for better operationality and stability. An ultrasonic motor was used for steering the mobile platform instead of the prior DC motor. The benefits of the ultrasonic motor enable the new platform to reduce its backlash in steering. A supporting plate and an active ankle joint attached to each mobile platform contribute stability when traveling in the standing position. The authors show the experimental results using new mobile platforms.

The paper demonstrates novelty and originality of ABLE in its composition, which enables a person with disabled lower limbs to travel in a standing position on a pair of small mobile platforms. This system is regarded as a biped‐type leg‐wheeled robot system that has high energy efficiency and good mobility for steps because of its wheels and legs; moreover, it has a pair of crutches for stability.

The purpose of this paper is to introduce a quadruped robot strategy to avoid tipping down because of side impact disturbance and a control algorithm that guarantees the strategy can be controlled stably even in the presence of disturbances or model uncertainties.

A quadruped robot was developed. Trot gait is applied so the quadruped can be modelled as a compass biped model. The algorithm to find a correct stepping position after an impact was developed. A particle swarm optimization-based structure-specified mixed sensitivity (H₂/H_∞) robust is applied to reach the stepping position.

By measuring the angle and speed of the side tipping after an impact disturbance, a point location for the robot to step or the foothold recovery point (FRP) was successfully generated. The proposed particle swarm optimization-based structure-specified mixed sensitivity H₂/H_∞ robust control also successfully brought the legs to the desired point.

A traditional H_∞ controller synthesis usually results in a very high order of controller. This makes implementation on an embedded controller very difficult. The proposed controller is just a second-order controller but it can handle the uncertainties and disturbances that arise and guarantee that FRP can be reached.

The first contribution is the proposed low-order robust H₂/H_∞ controller so it is easy to be programmed on a small embedded system. The second is FRP, a stepping point for a quadruped robot after receiving side impact disturbance so the robot will not fall.

To achieve stable gait planning and enhance the motion performance of quadruped robot, this paper aims to propose a motion control strategy based on central pattern generator (CPG) and back-propagation neural network (BPNN).

First, the Kuramoto phase oscillator is used to construct the CPG network model, and a piecewise continuous phase difference matrix is designed to optimize the duty cycle of walk gait, so as to realize the gait planning and smooth switching. Second, the mapper between CPG output and joint drive is established based on BP neural network, so that the quadruped robot based on CPG control has better foot trajectory to enhance the motion performance. Finally, to obtain better mapping effect, an evaluation function is resigned to evaluate the proximity between the actual foot trajectory and the ideal foot trajectory. Genetic algorithm and particle swarm optimization are used to optimize the initial weights and thresholds of BPNN to obtain more accurate foot trajectory.

The method provides a solution for the smooth gait switching and foot trajectory of the robot. The quintic polynomial trajectory is selected to testify the validity and practicability of the method through simulation and prototype experiment.

The paper solved the incorrect duty cycle under the walk gait of CPG network constructed by Kuramoto phase oscillator, and made the robot have a better foot trajectory by mapper to enhance its motion performance.

This study analyzes whether industry relatedness between a corporate borrower and its group peers significantly affects that firm's borrowing cost.

A regression analysis is run on bank-loan data of a sample of Indonesian companies for 2010–2020. The main variables of interest are the natural logarithms of the borrowing firm's number of affiliates classified within either similar 2- or 4-digit GICS industries, and the Caves weighted index of these firms' related diversification. This index measures how firms in a group are diversified in relation to the borrower. The dependent variable is the all-in credit spread, stated in basis points, over the LIBOR or similar benchmark, as of the loan issuance date.

Findings support the industry-relatedness hypothesis and contradict the risk-reduction hypothesis and show that banks charge lower loan spreads on a borrowing firm that either operates within a similar industry as its affiliate or diversifies into related sectors or industries. Consistent with the co-insurance-effect hypothesis, the results also underline the importance of the parent and first-layer firms as supporting instead of the tunneling vehicles within business groups. These conclusions hold even after segregating the sample and using the loan maturity as the dependent variable.

This study uses a unique diversification measurement based on the borrowing firm's sector or industry, relative to other group members, and offers new insights on business group diversification and bank loan costs.

This study aims to establish a bio-inspired controller for realizing the bounding gait of a quadruped robot system presented in this paper.

The bio-inspired controller is divided into three levels to mimic the biological patterns of animals. First, the high-level sub-controller is equivalent to the cerebellum, which could plan and control the motion of animals. Second, the effect of the middle-level sub-controller corresponds to the central nervous system. The central pattern generators in the spine generate the stable and cyclic signals as the fundamental rhythm for periodic motion of the leg and spine joints. Third, the low-level sub-controller is equal to the end effector, which adopts the simple proportional-derivative (PD) control to realize the specific motion trajectory of the legs and spine.

Combined with the stability criterion presented previously and the delayed feedback control method, the bounding gait of the cheetah virtual prototype could be actuated and stabilized by the bio-inspired controller. Moreover, the bio-inspired controller is applied to realize the bounding gait of an SQBot, which is a quadruped robot with a spine joint. Meanwhile, the validity and practicability of the bio-inspired controller for the control of quadruped robot have been verified against different forward velocities.

The bio-inspired controller and bionic quadruped robot system are instructive for the designing and actuating of the real quadruped robot.

This paper aims to imitate a cownose ray to develop a fish robot with paired flexible multi-fin-ray oscillating pectoral fins (OPFs) and control it to accomplish vivid stable 3-D motions using central pattern generators (CPGs) and fuzzy algorithm.

The cownose ray’s asymmetric sine-like oscillations were analyzed. Then a cownose-ray-like fish robot named Robo-ray was developed, which has paired flexible multi-fin-ray OPFs to actively control the fin shape and two tail fins to control the depth. To solve the problem of coordinated control for multi-degree-of-freedom Robo-ray, CPGs were adopted. An improved phase oscillator as a CPG unit with controlled amplitude, phase lag, smooth frequency transition and asymmetric oscillation characteristic was established. Furthermore, the CPG-fuzzy algorithm was developed for vivid stable 3-D motions. The open-loop speed control, the closed-loop control of depth and yaw were established.

The kinematic comparisons indicate that Robo-ray imitates the cownose ray realistically. The experimental results of closed-loop are obtained that the depth error of Robo-ray is less than ±100 mm and the course error is less than ±3°. Furthermore, the comprehensive experiments demonstrate that Robo-ray has high mobility, stability and robustness.

This research makes the fish robot with OPF propulsion closer to practical applications in complex underwater environment, for instance, ocean explorations, water quality monitoring and stealth military reconnaissance. In addition, Robo-ray can be taken as a scientific tool for better understanding of the hydrodynamics of OPF batoid.

This paper aims to develop a robofish with oscillating pectoral fins, and control it to mimic the bionic prototype by central pattern generators (CPGs).

First, the oscillation characteristics of the cownose ray were analyzed quantitatively. Second, a robofish with multi-joint pectoral fins was developed according to the bionic morphology and kinematics. Third, the improved phase oscillator was established, which contains a spatial asymmetric coefficient and a temporal asymmetric coefficient. Moreover, the CPG network is created to mimic the cownose ray and accomplish three-dimensional (3D) motions. Finally, the experiments were done to test the authors ' works.

The results demonstrate that the CPGs is effective to control the robofish to imitate the cownose ray realistically. In addition, the robofish is able to accomplish 3D motions of high maneuverability, and change among different swimming modes quickly and smoothly.

The research provides the method to develop a robofish from both 3D morphology and kinematics. The motion analysis and CPG control make sure that the robofish has the features of high maneuverability and camouflage. It is useful for military underwater applications and underwater detections in narrow environments. Second, this work lays the foundation for the autonomous 3D control. Moreover, the robotic fish can be taken as a scientific tool for the fluid bionics research.