We proposed a method for calculating the force applied to a joint when an external force is applied to a paw in a multi-link system, using the partial Lagrangian method and automatic differentiation. We compared our method with the Newton-Euler method and confirmed that the results were consistent, indicating that there were no algorithmic errors. The advantage of this method is that it can be analyzed algorithmically and can be easily applied to models with multiple degrees of freedom. To demonstrate this, we checked the change in the computed graph as the number of links increases, and confirmed that the graph is connected even when the number of links increases. Simulations were also conducted to confirm the generation of trajectories when external force is applied to the paw for a 10-link model, and it was confirmed that the effect of external force can be easily analyzed even for a multi-link model.

This paper proposes a hierarchical motion generation model that integrates individual intent into dynamic locomotion control, aiming to reproduce transitions between walking and running within a unified physical framework. The model consists of a strategy layer that reflects high-level objectives such as speed and energy efficiency, and a tactics layer that adjusts physical parameters such as leg stiffness, touchdown angle, and applied force. These layers interact through dynamically modulated control gains, allowing motion transitions to emerge naturally without explicit switching mechanisms. Simulations based on an extended Spring-Loaded Inverted Pendulum (SLIP) model demonstrate that differences in acceleration duration and energy supply result in diverse locomotion patterns. Notably, a transition from walking to running occurs when both acceleration intensity and additional energy surpass specific thresholds. The results highlight the model’s capacity to capture hysteresis-like features in human gait transitions and emphasize the importance of coordinated tactical control. Future work will address integrating multiple tactical elements and experimental validation toward applications in assistive robotics and human movement analysis.

This study aims to explore the potential of a reconstructive approach in detecting and analyzing hemiplegia in human walking motion using a musculoskeletal model. Hemiplegia, a neurological disorder characterized by partial paralysis of one side of the body, is a common complication of stroke that can significantly impact its victim's mobility and overall quality of life [10]. We employed a combination of surface electromyography (sEMG) and motion capture data collection techniques to study healthy individuals' muscle activation and kinematics both in normal conditions and while wearing a hemiplegia simulator. The collected data were analyzed using a non-negative matrix factorization (NMF) algorithm to decompose the muscle acti-vation into distinct muscle synergies and associated weights. We then compared the number of muscle synergies used between the healthy and simulated hemiplegia conditions to identify changes in muscle coordination patterns. Using the information obtained from the comparison, an attempt was made to construct the synergies of the hemiplegia gait from the synergies of the healthy gait by adjusting the weights. The results of this study suggest that a reconstructive approach is a feasible tool for detecting and analyzing hemi-plegia in a human walking motion. Furthermore, this study provides a framework for understanding the underlying muscle coordination patterns in hemiplegia and can serve as a basis for developing new rehabilitation strategies. This study is expected to contribute to the advancement of research in this field by providing insights into the neural control of human walking motion.

This study aims to construct a running simulator based on a motion generation and control system that enables the description of motion strategies using the spring-loaded inverted pendulum (SLIP) model. The problems of stability and robustness encountered in the running simulation with the SLIP model are elucidated, and stable running is achieved by controlling the stiffness and the attitude angle dynamically at touchdown, as well as human energy adjustment that is introduced to consider the active motion strategy. As a result, passive and active control by humans can be expressed, and a framework that can express the changes in running due to motion strategies is constructed. Finally, we discuss the possibility of describing and elucidating the motion strategies.

Human running motion is a complex motion that not only based on the movement of legs but also needs the entire body to participate in. Therefore, we focused on the upper body, designed a trunk and pelvic rotation assist suit to apply an external force on the chest and pelvis for assisting the running motion, changing the energy flow between the upper and lower body to improve the running efficiency. However, human motion is very complicated and difficult to analyze, it is hard to explore the specific effect of the external force which is provided by the rotation assist suit on human motion. In this paper, we proposed an advanced spring-loaded inverted pendulum model for simulating the human running motion in natural running status and expanded running status in which the motion is expanded by wearing the trunk and pelvic rotation assist suit, parametrically represent the changes of human due to the intervention of the external force, and discuss the effect of the external assistant force on the human running motion.

The aim of this study was to develop a walking assistance device by controlling trunk and pelvis motion. Human gait motion is a whole-body exercise that includes both lower body and upper body motion. Therefore, focusing on trunk and pelvic rotational motion, assist and resist the walking by applying external forces. By introducing periodic input control, control the timing of the supplementary force, and assist the walking. As an experimental result, the walking assistance improves gait by decreasing energy loss, and the walking resistance applies a load during walking.

Studies suggest that the level of muscle activation may influence force reproduction. The purpose of this study was to develop a sensorimotor-enhancing suit (SEnS)-unpowered assistive clothing without actuators or electrical devices-and to examine its efficacy for reducing voluntary muscle activation and improving force reproduction in the upper limb in healthy young adults. The SEnS was made of elastic fabric and designed to produce assistive shoulder flexion moment that can partially mitigate the required activation of the user's shoulder flexor muscles. A series of human experiments were then conducted in healthy young adults. As a proof of concept, reduction in force reproduction performance of the shoulder moment was confirmed with mitigation of the shoulder moment by using an external string. To examine the efficacy of the SEnS, voluntary muscle activation and force reproduction performance was examined with and without using the SEnS, by comparing the amount of activation in the shoulder flexor muscles and the error in force reproduction in the upper limb. The results showed that wearing SEnS reduced muscle activation and force reproduction error. These results suggest that the accuracy of force reproduction can be improved substantially by partially mitigating the shoulder moment and associated voluntary muscle activation, using the SEnS.

Anteflexion is essential for many physical activities ranging from carrying objects through snow shoveling to farm work. However, lumbago is a common cause of anteflexion, in which lumbar disks are under a heavy load due to changes in lumbar spine shape. With the aim to reduce lumbago risk, in this study we developed a motion sensor system that can estimate the shape, posture and load on the lumbar spine from measuring the lumbar in the lumbar region when the lumbar spine shape changes and the pelvis posture angle changes. We present a wearable version of this sensor system, and propose an estimation method of the lumbar shape using the pelvis posture angle and lumbar region skin curvature from this system. In addition, we measure the anteflexion using this system and study the change in load of the lumbar spine caused by changes in posture.

This paper presents a basic study on feasibility of usage of humanoid robots as an evaluator of assistive devices, by taking advantage of its anthropomorphic shape. In this new application humanoid are expected to help evaluation through quantitative measures, which is difficult with human subjects, and also to reduce the burden coming from ethical concerns with costly tests by human subjects. Taking a passive supportive wear “Smart Suit Lite” designed to relieve the load at lower back as an example, we have conducted pilot experiments by using the humanoid robot HRP-4C. The motion to be performed by the humanoid is obtained through retargeting technique from measured human lifting motion. The supportive effect is first estimated by simulation taking into account the mechanism of the supportive device. The experimentation of humanoid hardware brought us encouraging results on the basic feasibility of this application, as we observed a clear decrease of the torque for lifting when wearing the device as expected by the simulation.

The vastness of vineyards in Hokkaido makes it hard for workers to eradicate weeds. To solve this problem, the aim of the current research has been to develop a weeding robot with a multi-link manipulator that uses a stereo camera system as a visual sensing tool for recognizing grape stems. However, the accuracy of this technique is lacking due to unavoidable measurement errors from the stereo camera system. In consideration of this problem, a method that defines the grape stem area has been devised. Additionally, to compensate for errors in the visual sensing technique, a tactile sensing technique has been employed that can haptically recognize a grape stem by means of a multi-link manipulator. In this paper, a robust sensing system is reported that analyzes the displacement of a grape stem to detect it base position such that weeding can be performed.

This paper describes an analysis of the power assist and the skill assist effects of a semi-active assist mechanism based on an energy control. For this mechanism, we have developed a soft and flexible power assist device that consists of an elastic material and a small direct current motor. The assist force is then the elastic force, which is controlled by adjusting the length of the elastic material by means of the motor. The skill assist is based on a motion correction method of periodic motions that was developed in a previous study. The control method can provide both power assist and skill assist affects. In this study, we analyze the adequacy of the power assist when simultaneously applying the skill assist.

In this paper, we report the development of a power-assisted valve for fire engines. In Japan, the number of fire fighters is decreasing year by year; therefore, it is important to reduce the amount of labor involved in firefighting. Although the development of an automatic system is possible in strictly technical terms, firefighting regulations in Japan require that the valve be operated by hand. In this study, we aim to develop a power-assisted system that can be controlled in accordance with the intent of the operator. First, we confirm a relationship between the impedance parameters and valve opening time. From this relationship, we propose a method for predicting the valve opening time based on the initial value of the operation torque. Evaluating this method, we found that the average operation torque and average tracking error are improved by a factor of two. Second, we reduce prediction error by using a real-time prediction method. While a prediction method based on initial torque can adjust parameters only once, the proposed real-time prediction method can update parameters continuously. As a result, the evaluation score of the method improved from 0.55 to 0.35, and average prediction error was improved from 295ms to 205ms.

In recent years, information technology has made remarkable advancement and found increasing, applications in various fields. In the medical field, computer is playing a more important role in assisting the disabled. However, the interface between the disabled and a computer is usually composed of push button and touch sensors that are difficult of use. This research aims to develop a more user-friendly wearable interface using a MEMS (micro electro mechanical system) accelerometer and an optical fiber shape sensor that enable the disabled to use a computer more effectively. To demonstrate the application of this wearable interface, we developed several systems including a sensor fusion system for detecting motion of a human body, a communication device for the disabled to control computer keyboards and appliances, and a rehabilitation device referred to as a data glove. The effectiveness of the interface is demonstrated through several field tests.

We have designed the ultrasonic muscle activity sensor as a small sensor device, and the sensor can be built in the sensor suit for human machine systems. Measuring a change of the ultrasonic in muscles with this sensor, we have shown it's possible to estimate muscle force. In this study, we aim to design the algorithm that estimates the joint torque of knee with ultrasonic muscle activity sensor. Beside, in order to attain the generality of sensor suit, we also aim to examine the influence of constitutional differences, such as a physique index and a rate of body fat. Furthermore, we tried to obtain the basic data in order to the construction of system which can adjust individual difference.

The authors have developed innovative soft sensor suits embedded with electromyogram (EMG) and a variety of sensors for measuring human muscle activities. The sensor suits serve as a man-machine interface for human power amplification. This paper focuses on the EMG part of the sensor suits to study the fundamental issue of torque estimation based on the sensor readings. An innovative auto-calibration system is developed in this study based on multi-regression analysis and neural networks, where an universal database, rather than individual database for each operator, is proposed and as a result, the calibration time is dramatically decreased. The calibration system can also compensate for sensor positioning errors. In the end, the sensor suits are applied as a man-machine interface for a soft power amplifier composed of artificial muscles. The artificial muscles are successfully controlled using the torque information estimated by the EMG sensor suits. The relation between torque estimation errors on sensor suits and maneuverability of power amplifier is experimentally verified.

In order to provide quality care for aged and disabled people without causing physical and mental burden to patients and nurses, we have developed a prototype of a wearable typed robotic system, named HARO (Human-Assisting Robot), that is operated by a nurse to amplify his or her physical power. This paper proposes a design method of force control system with consideration of transition of interaction force to a patient during certain nursing motion.

This study aims to develop the fibrous optical actuator including the photochromic molecules, which isomerize in reversible by optical energy. This actuator is expected to be eco-friendly, lightweight, small-sized, flexible and noiseless. In this paper, we produce the prototype by diffusing /spl beta/-carotene in the crystal structure of nylon-6 filament. We investigate the feasibility of the proposed actuator to apply to robots and mechatronics experimentally.

The structure of hardware and software of AI control system of a mobile robot for service use are described. Hardware of the mobile robot described include an autonomous wheel vehicle and a five degree of freedom manipulator. The software of the AI control system is based on soft computing including fuzzy control rules, fuzzy neural network and genetic algorithms. The intelligent control of cooperative motion between the autonomous vehicle and manipulator realises flexible operations such as navigation of a mobile robot in presence of static and dynamic obstacles, processes of opening door in rooms and pushing buttons of an elevator. New hierarchical structure of the AI control system includes direct human-robot communication line based on natural language and cognitive graphics, and a generator of virtual reality for simulation of artificial life conditions for the mobile service robot. Simulation and experimental results of navigation and technical operations with the manipulator mobile service robot used in office building are described.

The intelligent mobile robot for service use with manipulators are moved in unstructured environments. Strategy for planning, environment recognition using two kinds of sensors and locomotion control to realize autonomous locomotion of the mobile robot are described. Fuzzy qualitative simulation, GA and hierarchical node map have revealed their effectiveness for path planning of the mobile robots. The results of fuzzy robot control simulation, monitoring and experimental investigations are presented.