Electronic components inside integrated module is designed to endure harsh thermal condition. Information about interior temperature and heat sources is then crucial for the optimal design of the electronic components. However, because of the compact design and internal position within the housing, it is difficult to experimentally measure the heat sources and internal temperature. To handle this issue, this study presents a method for estimating the heat source and internal temperature distribution via an inverse heat conduction problem. A sequential time domain approach with Tikhonov regularization is employed to predict equivalent heat sources of motor and MOSFET from a few and noisy measured temperature data. Krylov subspace-based finite element model reduction is also utilized to increase computational efficiency of the proposed framework. As a result, the suggested IHCP framework can be synchronized with sensor systems, including thermocouples and can provide the essential information such as unmeasured heat sources and temperature contour. A 200 W BLDC motor drive module for a collaborative robot is taken into consideration to validate the suggested approach with a practical application. Well-designed experimental tests using the BLDC motor drive module are used to assess the accuracy and efficiency of the suggested approach. A heat dissipation design of the BLDC motor drive is also carried out to show off a good application of the suggested method.

A variety of electronic products are in daily use to serve a variety of needs. Electronic products require different types of cable harnesses for production. Nowadays, user preferences vary and change quickly. Therefore, a variety of small-volume products are made, and producing various kinds of complex harnesses to satisfy people’s needs is difficult. In robotic automation, the wiring harness assembly process in the manufacturing of deformable objects is challenging. Because of the characteristics of a deformable object, the manufacturing task cannot be standardized. However, relying solely on image sensors is not advisable, due to the challenges involved in recognizing complex cables with image sensors. Additionally, even when cable recognition is possible, it requires too much time. To address these issues, this paper introduces a strategic algorithm for the wiring harness assembly process. The algorithm minimizes the dependence on image sensors by enabling the use of a robotic dual-arm system. The proposed method includes techniques such as cable estimation, frictional models, and trajectory planning in the algorithms. On the basis of these methods, for a provided assembly board, the algorithm outputs a systematic process for wiring harness assembly. Experimental results validate the algorithm, demonstrating its good performance.

This paper introduces a new development of a two-wheeled robotic wheelchair (TWW), designed to address the challenges of personal mobility for the elderly and individuals with lower limb disabilities. By incorporating a sliding seat mechanism and motorized support legs, the TWW enhances stability, comfort, and accessibility in narrow or uneven environments. Notably, the TWW has a minimum turning radius of 0.372[m], enhancing convenience in confined spaces. A dynamic inversion-based motion planner is developed to provide smooth and stable driving experiences by accurately converting user inputs into optimal trajectories. Furthermore, the system prioritizes safety through real-time fault detection, ensuring reliability in various scenarios. Experimental results validate the system’s enhanced posture stability and safety, highlighting its potential for a wide variety of applications in daily mobility and rehabilitation support.

This poster presents a whole body controller based on model predictive control (MPC), which enables a wheeled bipedal robot to demonstrate dynamic locomotion over various terrains including slope and stair, as well as under various types of external disturbances. To stabilize the robot's balance, optimal torques for each joint are generated through the MPC method. The proposed whole body controller was tested on the wheeled bipedal robot. Locomotive abilities are evaluated in the Gazebo simulator.

Wheels have been commonly used for locomotion in mobile robots and transportation systems because of their simple structure and energy efficiency. However, the performance of wheels in overcoming obstacles is limited compared with their advantages in driving on normal flat ground. Here, we present a variable-stiffness wheel inspired by the surface tension of a liquid droplet. In a liquid droplet, as the cohesive force of the outermost liquid molecules increases, the net force pulling the liquid molecules inward also increases. This leads to high surface tension, resulting in the liquid droplet reverting to a circular shape from its distorted shape induced by gravitational forces. Similarly, the shape and stiffness of a wheel were controlled by changing the traction force at the outermost smart chain block. As the tension of the wire spokes connected to each chain block increased, the wheel characteristics reflected those of a general circular-rigid wheel, which has an advantage in high-speed locomotion on normal flat ground. Conversely, the modulus of the wheel decreased as the tension of the wire spoke decreased, and the wheel was easily deformed according to the shape of obstacles. This makes the wheel suitable for overcoming obstacles without requiring complex control or sensing systems. On the basis of this mechanism, a wheel was applied to a two-wheeled wheelchair system weighing 120 kilograms, and the state transition between a circular high-modulus state and a deformable low-modulus state was realized in real time when the wheelchair was driven in an outdoor environment.

: In this study, gravity compensation of a wheelchair recliner was optimized to minimize the driving force of a recliner by adjusting the installation position of gas springs. The combined force of the gas spring and linear actuator compensate for the static load of occupant, where the force directions of the active and passive power sources cross each other inside the parallelogram links of the recliner. The optimal installation of the gas springs were determined via a non-linear optimization algorithm. The objective function of the algorithm involves simultaneous maximization of gravitational torque compensation by the gas springs and minimization of the average generated force of the linear actuators. The results showed that gravity compensation satisfies the condition of not exceeding the maximum force that the actuator can generate while maximizing the use of the passive force of the gas springs. The proposed optimization is expected to be used in various mechanical systems including parallelogram link structures.

Astrictive-type grippers, which generate gripping forces from adhesive forces at the contact surface, such as suction cup, are popular end-effectors as picking solutions because of their simplicity and small working space. However, the adhesive force of the astrictive gripper decreases with increasing complexity of the object surface; thus, its application has been restricted to simple picking of objects with a flat surface. Here, in this article, we present an all-round honeycomb astrictive gripper that has an orthotropic surface tension for grasping highly irregular shaped objects with an uneven surface. The design is inspired by mimicking the two-level (macro- and mesoscale) shape adaptation of the octopus's leg. The stiffness-variable structure is also consisted to change its stiffness similar to the function of octopus's leg, and owing to the combination of these structures makes possible to perform various tasks, including hammering, breakfast serving, and vaccination, which were not possible for previous astrictive gripper.

Stair climbing is necessary to improve the convenience of electric wheelchairs. An important issue in developing a climbable wheelchair is stability and speed during climbing. In this work, tri-wheel and supporting leg were adopted in the stair climbing method for high speed and stable posture. Based on the mechanical and static analyses of the climbing mechanism, the design method of the wheel cluster system was expressed as equations. These equations were proposed considering the design parameters that ensure the continuity and stability of the climbing motion. Moreover, the collision information between the stairs and the cluster system during the climbing motion was included in those equations. A validation test of the stair climbing mechanism was performed by manufacturing a prototype of 750 ( W ) x 800( D ) x 1,000( H ) mm 3 and 120 kg . The experimental verification proved that the electric wheelchair can stably go up and down the stairs under extreme conditions (stair width = 300 mm , stair height = 180 mm ) at a speed of 10 steps/min.

This paper presents a real-time trajectory planning method for highly dynamic tracking control of wheeled inverted pendulum (WIP) systems. A generic form of dynamic inversion problem for the class of WIPs is defined by combining a set of kinematic and dynamic differential constraints related to the system’s output expressed by the state variables, whose time evolution is to be sought as the solution of the trajectory planning. Instead of simply integrating forward the set of differential equations, which would lead only to an unbounded solution due to its non-minimum phase nature, an asymptotic expansion technique, transforming the original differential equations into a sequence of algebraic equations parameterized by the system’s characteristic constant, is used to allow for a stable and asymptotically exact solution of the dynamic inversion problem. To implement the proposed method for a real-time application where the reference command is not previously known, a command input filter is designed and applied to adjust the real-time input into a sufficiently differentiable reference command suitable for the inversion. Simulation and experimental studies are provided to validate the proposed method using our experimental WIP system.

To deal with the ill-posed nature of the inverse heat conduction problem (IHCP), the regularization parameter alpha can be incorporated into a minimization problem, which is known as Tikhonov regularization method, a popular technique to obtain stable sequential solutions. Because alpha is a penalty term, its excessive use may cause large bias errors. Ridge regression was developed as an estimator of the optimal alpha to minimize the magnitude of a gain coefficient matrix appropriately. However, the sensitivity coefficient matrix included in the gain coefficient matrix depends on the time integrator; thus, certain parameters of the time integrators should be carefully considered with alpha to handle instability. Based on this motivation, we propose an effective iterative hybrid parameter selection algorithm to obtain stable inverse solutions.

This article proposes a novel differential kinematics of elastic tendons for tendon-driven manipulators where tendons transmit actuator force/torque to remote links via a train of pulleys. The local variability of tension and longitudinal speed in each tendon is carefully investigated in terms of the rest lengths of the virtually partitioned tendon segments along the tendon. A significant attention is paid to building a proper friction-tension mechanic model between the pulleys and tendons to identify the no-slip points that are important to be used as kinematic constraints. The kinematic relations of tendon are obtained for two possible types of tendon-pulley transmission, i.e., free-free ended and fixed-free ended types, and then a complete kinematics of tendon is formulated by augmenting all the kinematic relations existing in the entire system. Simulation and experimental results are provided to validate the proposed kinematics of tendon by comparing with a previous simple spring model where the tension was determined by the relative positions of consecutive pulleys.

In this study, optimizing the mounting location of gas springs was proposed for an electric wheelchair with posture change unit to reduce the actuator torques. A simple parallelogram structure as lower part of the posture change unit structurally absorbs reaction torque from the upper part such that both parts of the seating unit can independently rotate without coupling each other. The optimization was therefore separately executed in each joint to compensate gravitational torque as much as possible by determining the optimal mounting position of gas springs. The gas spring specification and installation conditions were adopted from commercial products, and certain features of the specification were used as optimization constraints and boundaries. The results showed that the torques produced by the gas springs were largely balanced with the gravitational torques, indicating that the proposed optimization method could be used for parallelogram linkage system to efficiently work with less actuator torques.

In this study, we develop a novel damper prototype for robot manipulators of a mobile robot to perform rescue operations in extreme environments like battlefields. Shock vibrations occur when such robots drive over rugged terrain, adversely affecting both the robot and the rescued person. We propose a joint module that utilizes magnetorheological (MR) fluid to depress environmental impact vibrations. To do this, we first suggest a novel structure for our MR damper, with multiple working coils to augment the magnetic field intensity for the given volume; then, we perform dynamic simulations on the manipulator with the suggested MR damper installed, examining vertical impact acceleration and the driving torque generated in the joint module. The proposed damper can best reduce the amplitude of vibrations by about 90% at 21 Hz and by about 30% at the system's resonant frequency of 22 Hz, which are the frequencies of interest as those lie around the natural frequency of the robot arm.

In recent years, human-robot cooperation has enhanced productivity and achieved high payload, speed, and accuracy. Integrating typical industrial robots in human-robot cooperation is challenging because their arms may cause serious injuries to humans during a collision due to malfunction or errors due to robot operators. Therefore, counterbalance robot arms that are capable of counterbalancing the gravitational torques due to the robot mass have been developed to decrease the required capacity of the motors and speeds of these robots. In this research, we propose an advanced counterbalance mechanism using gear units and springs to improve the durability and reliability compared to the previously proposed wire-based counterbalance mechanism, which is difficult to apply to a commercialized product because it can easily be broken or stretched when an excessive force is applied for a long period. Moreover, our proposed method was extended to a multi-DOF system using a parallelogram mechanism based on a timing belt and pulleys to achieve multi-DOF robotic arms. A 2-DOF counterbalanced arm was designed to verify the effectiveness of the proposed mechanism. The simulations and experimental results showed that the proposed mechanism effectively reduced the gravitational torques of each joint of the multi-DOF arm.

Robotic grippers are essential components used in robots to perform certain tasks. Effective gripping capabilities are important for industrial and service robots. However, the parallel-type gripper, which is one of the most widely used robotic grippers, has limitations in terms of the objects that it can handle as well as applying the correct handling force, especially when handling fragile objects. Hence, a soft gripper fabricated using soft materials is proposed as a new alternative, with the advantage of preventing injuries when human-robot interaction is required. However, the limited holding force and uncontrollable movement of a soft gripper, due to its softness, could limit its use in real-life conditions. Therefore, in this article, we propose a shape-adaptive tip using a variable stiffness mechanism. To decrease the initial stiffness of the gripper tip, the reticulated polyurethane foam structure was embedded in the tip as the soft supporting layer to support the external force. The flexible mesh structure was applied as the jamming layer to change the stiffness of the tip. The prototype of the gripping system was tested, and the gripper could transfer the grape effectively without damage using the jamming mechanism.

Robotic manipulators require contact force sensing capabilities to sense the contact force between the manipulator and an object. Specifically, for humans and robots to coexist in the work environment, the robot must be able to detect an external force applied by a human. This study presents a new intrinsic force sensing method for robot manipulators that can obtain accurate information of the external force applied by a human during human–robot interaction. The method employs a robot cover, which is typically utilized in robot manipulators. Unlike conventional force sensing methods, a six-axis force/torque sensor is placed between the cover and the link of the robot manipulator. As a result, the proposed method provides information of the three-axis contact force applied to the cover surface and its contact location. Therefore, the cover itself becomes a sensorized cover based on the intrinsic force sensing method. To evaluate its sensing performance, the sensorized cover is experimentally validated using reference sensors. Finally, an experiment is performed in which the robot successfully recognizes letters written on the cover, indicating a high level of contact force sensing performance.

Increasing demand for automation and recent intact trends have accelerated the employment of robots in manufacturing and service areas. Thus, the need for an easy and efficient robot teaching is also increasing. In this paper, a novel concept of intuitive teaching device is proposed to overcome the weakness of the previous research that enables direct teaching by attaching the teaching device to the end effector of the robot and to improve the intuitiveness and operability. The teaching and collision prediction units are modularized according to their function and can be combined or disassembled. The manipulability is improved by lowering the height of the teaching device, and the influence on the payload is minimized by reducing the weight of the teaching device. A prototype is implemented, and the performance is verified through experiments by attaching the proposed teaching device to an industrial robot and performing teaching and playback tasks.

Compliance devices facilitate robotic assemblies by preventing excessive contact force on automated devices. However, the unavailability of displacement information regarding compliance devices makes it difficult to protect robots and objects during robotic assembly. It also limits repeatability and efficiency, especially regarding peg-in-hole and similar operations. We propose a six-axis displacement sensor installed on a remote center compliance device to detect the three translation and three rotation components generated by external forces and torques applied to the device, respectively. Triangular prism-shaped structures are used with capacitive sensing technology to measure the vertical and horizontal displacements in mm scale generated by the external normal and shear forces applied to the sensor. We designed and fabricated the sensor that could be integrated into a remote center compliance device, demonstrating it has a simple structure and is easy to install. To obtain six-axis force/torque information and six-axis displacement, calibration experiments were conducted using a specific setup and considering the device's geometry. The high sensing performance was verified through complementary experiments.

Robotic hands perform several amazing functions similar to the human hands, thereby offering high flexibility in terms of the tasks performed. However, developing integrated hands without additional actuation parts while maintaining important functions such as human-level dexterity and grasping force is challenging. The actuation parts make it difficult to integrate these hands into existing robotic arms, thus limiting their applicability. Based on a linkage-driven mechanism, an integrated linkage-driven dexterous anthropomorphic robotic hand called ILDA hand, which integrates all the components required for actuation and sensing and possesses high dexterity, is developed. It has the following features: 15-degree-of-freedom (20 joints), a fingertip force of 34N, compact size (maximum length: 218 mm) without additional parts, low weight of 1.1 kg, and tactile sensing capabilities. Actual manipulation tasks involving tools used in everyday life are performed with the hand mounted on a commercial robot arm.

The robotic gripper is an essential component for handling, manipulating, and transporting objects. However, the parallel rigid gripper, which is one of the most widely used grippers in robotics, has limitations in handling fragile objects with a proper gripping force. We present a shape-adaptive universal soft gripper that can grip complex-shaped fragile objects with a high holding force. The shape-adaptive skin of the gripper has extremely low stiffness ($\sim$46 kPa), even lower than that of tofu ($\sim$57 kPa); hence, it can inherently prevent damage to the object. In addition, only the area pressed by the object is selectively deformed, so the contact surface of the gripper can be deformed to match the target object contour. A stiffness transition in the gripper from a soft to hard state follows to achieve effective holding of the object, not just weak object hanging as the previous soft gripper. These characteristics are enabled by a sheet-shaped shape retention layer, a honeycomb-shaped soft supporting layer, and a four-sided wall structure to increase shear modulus. We present applications to show the performance of the gripper, including gripping tofu, preparing a cocktail with a squeezed lemon, and whole chicken soup.