Robotics has become one of the most important automation technologies for industry and society.

Robot components such as actuators and sensors, together with mechanisms and control systems, are being more and more combined with intelligent sensors in innovative industry design and fabrication. Robot technology is being applied in such fields as welfare, education, agriculture, and energy. Robot technology for welfare and nursing is being promoted by the government to increase lifestyle creativity as society ages.

This special issue focuses on robotics in fields from manufacturing industries to societal needs. Papers ranging from robotics theory to robot application have been invited. Among the topics covered are robot mechanisms, robot components, actuators, sensors, and controllers, robot control theory, robotic systems, energy saving, industrial applications, automation, vehicles, entertainment, medicine, welfare and nursing applications, and robotics education.

The 15 papers presented in this issue include actuators such as rubber artificial muscles or phase-change actuators, pneumatics, power assist devices such as assist glove and upper-limb assist devices, robotic suits, sensor fusion, omnidirectional locomotion, underwater robots, force display apparatuses, meal assistant robots, manufacturing applications of parallel-link mechanisms, surface polishing, and agricultural applications.

These papers bring readers the latest state-of-the-art robot technologies useful in everything from analysis and design to control and applications in innovative industries.

We thank the authors for their invaluable contributions and the reviewers for their advice – all of which have made this special issue both informative and entertaining.

Manipulating materials exposed to extreme temperature environments presents numerous significant challenges. For example, steel industries require new methods for the direct handling of materials at temperatures greater than 1000^◦C, and material scientists require new methods for handling specimens at the helium temperature, where high-quality analysis must be performed with very low levels of thermal noise. However, conventional actuators do not work in such environments because of their low thermostability and, more importantly, the loss of the magnetic and piezoelectric properties of the actuator materials. For example, it is well known that magnetism and piezoelectricity completely disappear at temperatures exceeding the Curie point. This paper proposes a new working principle for actuators based on the gas/liquid phase change of working fluids. We show possibilities for the actuator design, including selections for temperature-resistant materials and working fluids at various temperatures. In addition, we discuss the design of the first prototype actuator, which worked successfully at 180^◦C by utilizing the gas/liquid phase change of water. The basic experimental results show significant potential for the actuator.

This study aims to use three-dimensional (3D) Finite Element Modeling (FEM) to establish a quantitative design optimization method for McKibben-type pneumatic rubber artificial muscle. First, a simple 3D model that does not account for the friction between the tube and the fiber braid strands and or that between the strands themselves is developed. The model is validated through experimentation, and the usefulness of the model is examined. With this model, the effects of various parameters, e.g., the braid angle, on the operation of the artificial muscle is investigated. It is found that the characteristics of the artificial muscle can be predicted. Thus, the proposed analysis may be a useful design method for braided artificial muscles.

We have developed new articulated manipulators with compact pneumatic cylinders and high levels of structural flexibility and safety by adopting new structures. When a pneumatic cylinder is used as an actuator, mechanical friction and dead time are the main problems manifesting in the pneumatic servo system. In this study, we first designed nominal models of articulated manipulators using experimental data on a closed-loop system. Thereafter, we analyzed the kinematics of the manipulators and examined the method of generating the trajectory of a manipulator’s fingertip. Finally, we conducted simulation and experiments on the articulated manipulators we developed to understand their positional controllability. Furthermore, we experimentally evaluated the pressure-sensitive sensor embedded in the fingertip, the results of which are also reported in this paper.

Parallel-link robots are generally high in power and precision because of their parallel arrangement of actuators. However, they have a workspace smaller than that of serial-link robots. In this paper, we develop a parallel-link robot prototype with pneumatic linear drives in which a mechanism for varying the actuator inclination is incorporated to enlarge the workspace. Our parallel-link robot realizes the rotational and translational motions of the end effector principally by means of the linear reciprocating motions of pneumatic linear drives mounted on the base. Auxiliary pneumatic actuators are used to adjust the inclination angles of those main pneumatic linear drives. The use of pneumatic actuators to realize the proposed parallel-link robot results in a lightweight, compact, and low-cost construction. The workspace and motion transmissibility of our parallel-link robot are analyzed through simulations based on kinematics; then, experimental investigations are carried out using the prototype.

In this study, electromyography is applied to a subject’s forearm to discriminate between intended finger and wrist motions and the resulting signals are used to control a power assist glove. This glove is designed to assist with grasping. The fingers and wrist are moved when the corresponding muscles of the forearm contract simultaneously. Therefore, the intention to move either a finger or a wrist must be discriminated to enable assisting a finger movement by this glove. The introduction of Self-Organizing Maps (SOM) improves the ability to discriminate between these motions. In this study, the effectiveness of a discrimination method using SOM is verified experimentally.

This paper proposes a meal-assistance robot that uses ultrasonic motors (USMs) and an eye-interface. The proposed robot is designed with simple manipulators moving in orthogonal coordinate axes to avoid unsafe motion and vibration. With the application of USMs, the proposed robot has excellent features. In particular, because it does not interfere with other electronic devices, the proposed robot is satisfactory choice for medical and welfare facilities. Moreover, the proposed robot is designed to be controlled with an eye-interface, which makes this robot much easier to use than previous models. The structure of the robot is introduced and its effectiveness is confirmed by experiments.

This paper proposes an upper-limb power-assist machine that is driven by a single actuator to reduce its weight and cost. The assist machine is intended for supporting shoulder and elbow movements during work in the field of viticulture. It consists of an arm part, a mounting part, and a drive part, the last of which contains an actuator and a worm gear. The arm part is equipped with a parallel link mechanism. In order to realize natural upper-limb motion, the length of the arm part is designed on the basis of human upper-limb motion. The assist machine is controlled by user intention through the use of bending sensors attached to the input device. The assistance effectiveness of the proposed assist machine is verified experimentally by measuring the EMG signals of the deltoid, biceps brachii, and triceps brachii muscles.

In recent years, various robots have been developed that can be worn on the body. These can be used to assist elderly people and people with disabilities by either providing extra power or helping them with walking. These robots usually form an external skeleton around the frame of the body. Although the external skeletal structure has the advantage of supporting the robotic mechanism, an adjustment mechanism to match it to the contours of the wearer’s body is necessary, and this mechanism increases the weight of the robot. In this study, we propose a non-exoskeletal structure which uses the skeletal system of the human body, and we develop a lightweight robotic suit that gives little feeling of restriction.

In this study, a fingertip force display device that uses negative pressure is developed. The device can control the resisting force against a finger’s motion by regulating the negative pressure in an air chamber processed in the device. Information about the position of a finger is obtained with a Web camera using AR-Toolkit library, and the resisting force is controlled based on the fingertip position (velocity), which shows the capability of the VR-oriented application and mechanical impedance task. The effectiveness of the proposed system is verified through experiments.

A two-wheeled, self-balancing robot is proposed using 6-axis MEMS sensors MPU6050 to measure its posture. The sensors integrated with a 3-axis gyroscope and a 3-axis accelerometer, can output the inclination of the robot based on sensor fusion algorithm. A handheld remote controller sends out commands to the robot such as forward, back, and turning around. According to the inclination and orientation commands, a 16-bit MCU using the PID control algorithm calculates the required control voltage for the motors, to adjust the robot’s posture and keep the body balanced. In this paper, the principle of the sensor fusion algorithm is fully described, and its effects are verified through related experiments. The experimental results show that the proposed robot is practical and able to balance using inexpensive MEMS sensors.

This paper describes a new pneumatic rubber leg mechanism for omnidirectional locomotion. The new mechanism was adopted from a pneumatic balloon actuator where translation and bending motions are produced as a result of balloon deformation. It was constructed using five chambers: one on the top and centered over four bottom chambers arranged in a square. Several possible designs were simulated to achieve the optimal design using a non-linear finite element analysis that considered the design parameters and the geometrical and material non-linearity of the elements. Prototyping was then performed using a rapid and efficient silicone rubber molding fabrication process based on computer-aided design and manufacturing. The experimental results were in good agreement with the analytical results. In conclusion, we have established a new rubber leg mechanism with a high degree of freedom to realize omnidirectional locomotion for a soft robot base, delicate object conveyance, and / or microscope stage applications.

Although, Autonomous Underwater Vehicles (AUVs) used for investigating underwater ecology have attracted the attention of underwater researchers, conventional AUVs moved underwater by screw propellers generate loud noise that may disturb the underwater environments and inhabitants to be observed. This paper discusses the development of an AUV that mimics the manta ray. Central Pattern Generators (CPGs) are also proposed to generate the motion of pectoral fins for Manta robot. The practicality of the robot is checked in underwater propulsion experiments, and the effectiveness of the proposed motion generation method is demonstrated in numerical simulations.

A mobile quality evaluation robot has been developed to make agricultural products traceable. The operator moves the robot along a crop line to harvest fruit. The quality of the harvested fruit is evaluated from images taken by a machine vision system mounted on the robot. At the same time, individual plants from which the fruit was collected are identified from the plant numbers of IC tags attached to every one. A field map with information about fruit quality and yield is created based on these data.

This paper proposes a novel diamond tip burnishing process to improve the integrity of various free-curved surfaces using a spherical 5-Degree-Of-Freedom (5-DOF), hybrid parallel mechanism. The developed parallel mechanism, which has high rigidity and a large workspace, is composed of a spherical 3-DOF parallel mechanism and an XY stage, and is equipped with a burnishing tool on its output link. Using a three-dimensional force control system, the parallel mechanism can adjust the thrust force in the burnishing process. The surface roughness and profile of the stainless steel (AISI 316) workpiece, burnished by the proposed method, were evaluated. The surface integrity depended on the values of cross-feed and thrust force, which were controlled by the hybrid parallel mechanism. In addition, the surface roughness improved as cross-feed decreased and thrust force increased. The preliminary surface roughness of Ra = 2.5 μm was improved to Ra = 0.25 μm in the burnishing process of the free curved surface, and homogeneous surface integrity was obtained. The results thus suggest that the proposed burnishing method can achieve a high-quality surface finish, even on a free curved surface.

Our ultimate goal is to develop an automatic polishing system that uses an industrial robot equipped with whetstones. The robot mimics the movements skilled workers make as they polish surfaces manually. This paper, the first step in the development of our system, presents experimental results to prove that our system completely removes the marks, which is the most time-consuming and crucial process for human workers, from the flat surfaces of metallic molds produced through the Electrical Discharge Machining (EDM) process. We build a polishing system that consists of a small 6-DOF industrial robot for material handling. Attached to its wrist is a six-axis force-torque sensor and it employs a whetstone holding mechanism. Before the robot system begins its polishing work, the normal force to be applied to the flat surface can be adjusted to a target value by altering the height of the hand. We adopt two polishing paths for the whetstone, reciprocating and zigzag. We then conduct experiments using the two paths, visually inspect the surface, and measure the surface roughness and shape. Based on the experimental results, we confirm that the system has completely removed the EDM mark layer. Although we find that the zigzag path leaves striped patterns on the polished surface, we are not able to determine their cause. Finally, we test three combinations of the two paths under different conditions to find the most suitable combination.

Vibration-free motion in minimal time is desired for industrial robotic applications. Hence, these criteria have to be considered during trajectory planning for a robot arm, wherein polynomial splines are often used for interpolating the trajectory through several via points. Among polynomial splines, the cubic spline is the lowest-degree spline that can provide jerk limitation, a feature that is important for reducing vibration during motion. However, using jerk limitation alone does not eliminate vibration completely and sometimes restricts the performance of industrial robots. This paper proposes an implementation of cubic spline optimization with free via points for reducing motion time, combined with input shaping for suppressing vibration. Experiments are conducted on a semiconductor wafer transfer robot arm to demonstrate the effectiveness of the proposed approach.

Recently, the use of microchannel chips in micro total analysis systems, which can provide savings of natural resources and energy, has attracted attention in the medical field. Generally, the photolithography technology used in semiconductor manufacturing is used to manufacture microchannel chip dies. However, it involves several processes such as mask fabrication and the application of a photoresist to Si substrate, as well as expensive clean room facilities. In light of this, methods to form a fine groove using a micro-endmill are examined. The effects of the tool run-out of a few micrometers on micro-endmilling, as well as on the groove accuracy of a microgroove, are examined.

In the assembly, efficient part feeding is a decisive factor for a successful automation. Therefor an automated modular and part-flexible feeding system for micro parts on the basis of piezoelectric vibratory conveyors has been developed at the wbk Institute of Production Science. Very different parts can be conveyed, positioned and partly be rotated around their vertical axis by the system. The sliding conveyance offers also the possibility to feed extremely delicate parts. In this article the design and the commissioning results of the system are presented. In the end an outlook is given on future work to increase productivity and efficiency of the system.