Human work and life support are areas that provide practical applications for robotics and mechatronics technology. There is great expectation from the industry in these fields, and research and development efforts have been actively undertaken with great social impact. To support human work and life accurately, we must understand the complicated sensory, nervous, and motor control systems that enable design and development of appropriate assistive devices.

Therefore, in this mini special issue, we focus on robotics and mechatronics for human sensing, modeling, and augmentation.

The editor hopes that this special issue will attract researchers’ interest and contribute to further developments in this field.

A forward bending motion is essential in everyday tasks, such as carrying objects, shoveling snow, and performing farm work. However, many people suffer from lumbar pain resulting from forward bending motion, which causes a lumbar disc load owing to the changing of the lumbar shape. We have developed a wearable lumbar load estimation system, which measures the skin shape on the back using a curvature sensor. Because the lumbar load varies with the external load, the lumbar load should be estimated based on the external load. Therefore, we have developed a method for estimating an unknown external force using a muscle stiffness sensor. Muscle strength can be estimated by measuring the muscle hardness from the surface, and the relationship between the external force and the muscle force can be modeled. Using this method, we estimate the dependence of the lumbar load on external forces in real time. In addition, we simplify the calculation by converting the external load into a load resulting from a person’s own weight. We incorporate the proposed method into our wearable sensor system, estimate the lumbar load, and compare this with the results of a musculoskeletal dynamics simulation.

As the demand for nursing care services is growing, the physical burden involved in caregiving has drawn widespread attention. To mitigate the physical burden in caregiving, we have to recognize what kind of work and problems are involved in each caregiving task. To identify the problems involved in caregiving, we need to recognize the work and analyze its workload. Aiming to reduce the burden on the waist during caregiving tasks, we are developing inertial sensor suits for measuring the working motions. With the developed method, the burden on the waist is estimated from the waist posture. Considering its use in practical caregiving sites, the number of inertial sensors should be the minimum necessary, which depends on the number of body parts where to measure the posture. In this study, we select the body parts to achieve the two above-mentioned goals: to recognize the work involved in caregiving and capture the waist posture. A support vector machine (SVM) is used to recognize the work. Its conventional method of selecting the features on which to recognize the work only considers the recognition accuracy and does not sufficiently meet the needs for measuring the postures. Therefore, we propose a new feature-selection method, which can evaluate the waist-posture measuring accuracy and can make forward feature selections in the same manner as the conventional wrapper method. We have verified the effectiveness of the proposed method by measuring simple simulated work motions.

In this paper we discuss the active and passive nature of the assistive wearable gait augment suit (AWGAS). AWGAS is a soft, wearable, lightweight, and assists walking gait by reducing muscle activation during walking. It augments walking by reducing the muscle activation of the posterior and anterior muscles of the lower limb. The suit uses pneumatic gel muscles (PGM), foot sensors for gait detection, and pneumatic valves to control the air pressure. The assistive force is provided using the motion in loop feedforward control loop using foot sensors in shoes. PGMs are actuated with the help of pneumatic valves and portable air tanks. The elastic nature of the PGM allows AWGAS to assist walking in the absence of the air supply which makes AWGAS both active and passive walking assist suit. To evaluate the active and passive nature of the AWGAS, we experimented to measure surface EMG (sEMG) of the lower limb muscles. sEMG was recorded for unassisted walking, i.e., without the suit, passive assisted walking, i.e., wearing the suit with no air supply and active assisted walking, i.e., wearing the suit with air supply set at 60 kPa. The results shows reduction in the muscle activity for both passive and active assisted walking as compared to unassisted walking. The pilot trials of the AWGAS were conducted in collaboration with local farmers in the Hiroshima prefecture in Japan where feedback received is complementing the results obtained during the experiments.

As muscle weakness due to aging or fatigue potentially increases the risk of injuries or accidents, support wears may be needed that can play a role in assisting various motions. Recently, research and development of such support wears have gained momentum in order to measure a variety of their supporting effects. While in the research stage, they are designed and evaluated on the premise that they are carefully adjusted to fit the specific wearers’ physiques. However, in actually producing and using such support wears on sites, they pose a problem in that their supporting effects cannot sufficiently be felt because they are difficult to fix, or because they do not fit all body sizes. Therefore, in this study, we have quantitatively evaluated their assisting effects using simulations with a musculoskeletal model with a built-in functional underwear with support parts. In particular, we evaluated whether any differences in arrangement of support parts on the human body, due to their different fixture methods, will have an effect on their assisting effects. We have also developed a support wear, with easy to adjust support parts and fixture positions, and have verified the abovementioned simulation accuracies by myoelectric measurements. This verification found that the proposed simulation method can predict, to some extent, the impacts of any deviations in the support parts’ positions and their assisting effects.

This study describes the effect of Active Corset on the lumbar spine. Active Corset is assist tools used to prevent low back pain. It tightens the waist optimally according to the lumbar load during work. This study aimed to clarify the mechanical effect of tightening of the pelvis on lumbar joints and determine the mechanism leading to reduction of the lumbar load. Moreover, this study examined the phenomena commonly occurring among the subjects with reduced lumbar load by tightening of the pelvis. First, we will present some examples of currently used assist tools and demine the utility of the Active Corset among the various tools used. Next, the mechanism of the Active Corset will be described. Further, we will present a hypothesis about reducing the lumbar load by tightening the pelvis. After describing the change in the joint bending angle on tightening, we will describe reduction of burden from the antigravity torque around the lumbar joint. Finally, we will compare active tightening using Active Corset with tightening using a constant force and describe the advantage of active tightening.

Lower back pain is a major health concern worldwide. One cause of lower back pain is the burden on the lumbar region caused by handling heavy objects. The Ministry of Health, Labour and Welfare in Japan has recommended “squat lifting” to reduce this burden. However, this technique, which supports a large force on the lower limbs, is not very popular. Therefore, we aim to develop a power assist suit for squat lifting and propose herein a gastrocnemius-reinforcing mechanism. We also discuss the joint torque estimation from a motion analysis of squat lifting to construct a prototype. Finally, we describe the performance of the prototype when mounted on a human body. We found that when using the prototype assist suit, the %MVC (maximum voluntary contraction) of the gastrocnemius while performing squat lifting reduced by 48% compared to the value obtained without using the suit.

Parallel-wire driven systems, which use light flexible wires in place of rigid links, control the position of a target object by controlling their wire lengths. In the kinematics for such a parallel-wire driven system, when the relationship between the end-effector position and the wire lengths is investigated, a fixed point for the wire-contacting point on the winding reel in the actuator (or guide pulley) is often approximated to simplify the calculation. The approximated kinematics however could lead to a number of positioning errors in the positioning control. This study proposes a framework for evaluating these positioning control errors by using approximated inverse kinematics. In view of the system dynamics, this study analyzes the positioning control errors for the control method in the wire-length coordinates. We discuss a case study on a two degrees-of-freedom planar system using three wires.

In Japan, a rising number of endoscopic surgery operations have boosted an expectation for the development of a training environment for qualified surgeons. The endoscopic surgery operation requires the operator to operate forceps by hand based on two-dimensional operative field information displayed on the monitor. The characteristics of the operation include a lack of stereoscopic visual field information and movement of the tip of the forceps, which is symmetric about the trocar. These are issues that require an empirical solution from the operator. It is desirable that these issues have already been overcome before the operator starts practicing as an operating surgeon. To this end, it is effective to train the operator in the sensation of forceps operation, which associates the operative field vision with the forceps operation by hand. Therefore, this study includes digitizing the forceps operation by qualified surgeons and providing it to the trainee as visual and force information in order to build a training device that facilitates the cultivation of the sensation of forceps operation.

We propose an underwater image enhancement algorithm for improving underwater robot visibility. Images captured in underwater environments are typically degraded by the effects of absorption, scattering, and noise. Degraded images impede underwater robot task performance (e.g., inspection, detection, and visual simultaneous localization and mapping). In this study, we improve the underwater light model by considering floating particle noise and non-uniform illumination from artificial light sources. Specifically, a systematic underwater enhancement method that includes a floating particle removal algorithm and an image-dehazing algorithm is proposed. Our method is effective for underwater image enhancement applications in real-world scenarios. We compare and evaluate our proposed method with state-of-the-art methods, with an underwater evaluation and a feature-matching performance. The experimental results show that our method yields comparable (and even better) results than state-of-the-art methods.

Japan is located in a seismic zone and is hence affected by earthquakes, which necessitates frequent disaster rescue activities. It is difficult for humans to access the site of an earthquake with collapsed buildings for carrying out rescue operations. The use of various mobile robots to undertake such rescue activities in place of humans has been proposed and studied to cope with such situations. Disaster sites covered with debris contain narrow spaces and irregular terrains, where robots that can change its size and rigidity should be able to move more effectively. In this study, we propose a robot system, separated into multiple robot units and variable in size and rigidity by connecting and separating them, so that it can adapt itself to a diversity of environments. To realize the proposed robot system in both mechanical and control aspects, we prototyped a group of robot units that can move as well as get connected and separated. We evaluated its thrust and ability to traverse irregular terrains as well as the automatic connection of robot units using cameras and markers.

In this research, we consider a posture control problem of a planar two-link torque unit manipulator under a viscous friction condition. The torque unit is a module that consists of an electric motor and a reaction wheel. The friction caused by the presence of a viscous environment cannot be ignored in the real system. In this report, we first clarify the relation between the angle of links and the angular momentum of the reaction wheels under the viscous friction condition. Next, we try to control the first link at an arbitrary reference position without taking into consideration the angle of the second link. The angle of the first link can be controlled by changing the viscous friction condition between the first link and the base. Moreover, we attempt to control the second link at an arbitrary reference position by using the residual angular momentum of the reaction wheel at the second link. Finally, we demonstrate the feasibility of the proposed method by conducting a verification experiment.

For vehicle dynamics control and Autonomous Driving (AD) system, it is important to know the friction coefficient μ of the road surface accurately. It is because the lateral and the longitudinal force characteristics of the tire depend on the road surface condition largely. However, currently, it is difficult to detect tire performance degradation before the deterioration of vehicle dynamics in real time because tire force estimation is usually conducted by comparing the observed vehicle motion with the onboard reference vehicle-model motion. Such conventional estimators do not perform well if there is a significant difference between the vehicle and the model behavior. In this paper, a new tire state estimation method based on this tire longitudinal characteristic is proposed. In addition, the estimator for tire-road surface friction coefficient μ is proposed by using this geometric relationship. Using this method, the friction coefficient value for a real road can be determined from relatively simple calculations. Also, the advantage of this method is that it can be estimated in a small slip region before the tire loses its grip. In addition, this paper explain how to apply and the effect on the actual vehicle.

Our research group established a technology for forming three-dimensional cell constructs to regenerate osteochondro cells without scaffolding. The established technology employed spheroids to form cell constructs. We also developed a method for arranging spheroids in arbitrary positions to form cell constructs in complex shapes. However, we could only form cell constructs as expected when the formed spheroids were the appropriate sizes. This study, therefore, aimed to chronologically analyze the spheroid morphological characteristics of rabbit mechanical stem cells using the developed spheroid morphological evaluation system. We set the numbers of cells/wells as 2 × 10⁴, 3 × 10⁴, 4 × 10⁴, 5 × 10⁴, 6 × 10⁴, and 7 × 10⁴ and the passage number as 7. Further, we observed the cultured spheroids every 24 hours after seeding for five days. The analysis enabled us to specify an optimal range for the numbers of cells required to form spheroids with high degrees of circularity. We could also control the formed spheroid sizes by adjusting the cell count and culturing time.

Low-cost robotics, fully integrated in the corporate IT infrastructure, is a requirement in the era of modern industrial automation derived from the Industry 4.0 model. This paper presents a multidisciplinary robotics-based learning (R-BL) project consisting of the development of a modular control architecture and a gripper for small manipulators. The solution, as compared with options available in the current robotic market, is a balance between low-cost devices with industrial robot performance. The project is carried out as part of the Robotics and Mechanisms program, a course in the automation engineering degree program at the University of Brescia in Italy. A 4-axis small-size robot, able to manipulate many kinds of objects, was designed and built by a student team by integrating the controller and the gripper. The controller was implemented using a real-time Raspberry platform by following a modular design concept. The control software is characterized by a short development time. The gripper was advanced to achieve low cost and modularity tradeoffs.