Power assist devices are meant to be used in cooperation with humans. However, there are several variables that influence the human response and the actual systems rarely take into account the human features, hence failing to fulfill their potential. In this paper, the way that constraining and applying different lifting schemes affect the perceived weight of the lifted object is presented. The results of the experiment showed a correlation between the perceived weight and the restrained condition leading to a second experiment to determine if the grip force applied was related to the perceived weight. These results were applied in the creation and the experimental methods of the presented one-degree of freedom power assist device for lifting objects and its control algorithm. The objective of the aforementioned device was to enlighten the factors behind the difference in the perceived weights, found in a previous research, between lifting an unconstrained object and lifting it with a power assist device. As a result, a correlation was established between the reaction force and the perceived weight, focusing in the timeframe in which the object lost all contact with the support surface.

Generating motions for nursing-care assistant robot in hospital environment is a challenge. The cost of teaching an unexperienced user to operate the robot skillfully is very high. In this research a Discrete HMM (DHMM) is trained on samples of skilled operator and then the robot motions is reproduced by the DHMM and related algorithms generating optimum state sequence, Key Motion Frames (represented by discrete output symbols) and interpolated robot joint trajectories. The proposed motion generation method has a simple framework which allows the engineer customize the trajectories by editing key motion frames according to different requirements of tasks. This endows the robot the ability that utilize the skills of experienced operator adaptively in similar situations.

In this paper, we present the design and evaluation of a novel control method for a power assist robotic system for manipulating objects with it by human subjects. We consider the manipulation of objects in harmonic motion (object is lifted up and lowered down repeatedly) as we think that this motion may be very practical and useful in object manipulation. We develop a 1 DOF power assist system. The subjects manipulate different sizes of objects with the system in harmonic motion. We analyze human characteristics such as weight perception, load force, object motions etc. We find that the load force and acceleration are excessive that reduce the performances of the system. We then optimize the perceived heaviness. We then design and implement a novel control method based on human characteristics to reduce load force and acceleration. Results show that the novel control reduces load force and acceleration, optimizes perceived heaviness and thus makes the performances (maneuverability, safety etc.) satisfactory. We also compare this novel control designed for object manipulation in harmonic motion to another novel control designed for lifting objects with power-assist in linear vertical motion. Finally, we propose to use the findings to develop control method for power assist devices for manipulating heavy objects in industries that may enhance interactions between humans and robots.

A power assist robot reduces perceived weight of objects lifted with it. However, root cause of reduced heaviness and factors affecting the heaviness are still unclear though the knowledge on the root cause/factors could be used to modulate human's feelings and the interactions between human and robot. This paper investigated the causes/factors behind the reduced heaviness. We adopted two strategies for this. Firstly, we included weight perception in robot dynamics (and control) in such a way that the mass parameter of the inertial force was considered different from that of the gravitational force because the perceived weight is different from the actual weight. Secondly, we compared weight perception, load forces and motions for power-assisted manipulation to that for manual manipulation and identified some clues regarding the causes/factors of reduced heaviness. We found that perceived weight, load force and its rate, velocity and acceleration for power-assisted objects were lower than that for manually lifted objects. We observed time delays in position sensing, force sensing, servomotor etc. for the power-assisted objects, however, the delays were almost absent for the manually lifted objects. We argued that the delays were the root cause of reduced heaviness and the elements of the system contributing to the delays were the factors affecting the perceived heaviness. To cross-check it, we increased time constant of the servomotor and found that the increased time constant reduced perceived weight. The findings may be used to develop power assist robots for manipulating heavy objects in industries that may help improve/modulate interactions between robots and users.

We hypothesized that weight perception (WP) due to inertia might be different from WP due to gravity for lifting an object with a power assist robot (PAR). Objects were lifted with a PAR independently under three different lifting schemes-unimanual, bimanual, and cooperative lift. Then, psychophysical relationships between actual and power-assisted weights (PAWs) as well as excess in load forces (LFs) were determined for each scheme separately. A novel control strategy was introduced to reduce the excess in LFs for each scheme. Finally, we proposed to use the findings as design guidelines to design PARs for lifting heavy objects in industries that would improve HRI in terms of human, robot and system.

We developed a 1 DOF power assist robot for lifting objects. We hypothesized that human's perception of weight due to inertial force might be different from the perceived weight due to gravitational force for lifting an object with a power assist robot. We established psychophysical relationships between the actual weights and the power-assisted weights for the objects lifted with the robot, and also determined the excess in load forces that the subjects applied for three independent lifting schemes or grasp configurations: (i) unimanual lift, (ii) bimanual lift, and (iii) cooperative lift. We also compared the weight perceptual and load force features for the unimanual lifts to that for the bimanual and cooperative lifts. We then modified the power-assist control using a novel control strategy based on the weight perceptual and load force features. The control modification reduced the excessive load forces applied by the subjects in each lifting scheme and thus enhanced maneuverability, naturalness, ease of use, stability, safety etc. of the robot system significantly. Finally, we proposed using the findings to design human-friendly power assist robots for carrying heavy objects in various industries.

An object lifted with a power assist robot is always perceived lighter than its actual weight. But, the human operator cannot differentiate between the power assisted weight and the actual weight and eventually applies load force (vertical lifting force) according to the actual weight of the object. This faulty force programming (excessive load force) gives faulty motions to the power assist robot and jeopardizes its operability, maneuverability, ease of use, naturalness, human-friendliness, safety etc. In this paper we assume that these problems still exist with the power assist robots because human's weight perception is not included in the design and control of the conventional power assist robots .We hypothesize that human's perception of weight due to inertial force may be different from the perceived weight due to gravitational force for lifting object with a power assist robot. Based on this hypothesis, we designed a 1 DOF power assist robot and established a psychophysical relationship between the actual weights and the power assisted weights for the objects lifted with the robot. We also determined the excess of the load forces that humans applied. Then, we modified the control system of the power assist robot based on the psychophysical relationship and the load force characteristics. The modification of the control system reduced the peak load forces applied by humans and thus enhanced maneuverability, naturalness, ease of use, stability, safety etc. of the robot system significantly. Finally, we proposed using the findings to design human-friendly power assist robots for carrying heavy objects in various industries.

In this paper, we designed a 1DOF power assist system for lifting objects. Human's vertical lifting force, comprises of inertial force and gravitational force, was considered as the desired dynamics of the system. We hypothesized that human's perception of object weight due to inertial force might be different from the perceived weight due to gravitational force for lifting object with the power assist system. The hypothesis meant that the mass parameter of the inertial force might be different from the mass parameter of the gravitational force. We then designed the control system of the power assist system based on the desired dynamics and simulated the system using MATLAB. We then psychophysically determined the optimum mass parameters for the inertial and the gravitational force components of the desired dynamics of the power assist system on the basis of human's perception of object weight. The results showed that human's weight perceptual consideration with the dynamics (control system) of the power assist system enhanced maneuverability, stability, naturalness, ease of use, safety etc. when lifting objects with the system. Finally, we suggested using the findings to design human-friendly power assist systems for manipulating heavy objects in various industries.

the declining trend of population has given a growing problem in the future where the need to provide adequate healthcare for old people and person with disability with reducing human workforce. Therefore to address this issue, we are looking for a solution where human can cooperate with autonomous robot to reduce the workforce of providing these services. At present the majority of autonomous robots are mostly used in factories where speed and accuracy are given highest priority. In our research, we are focusing in the area where the robot that cooperate with human to lift or carry a human subject. In this area the robots are required to interact with human and move in such a fashion where it will move with human-like motion so that the human subject that is being move will not feel intimidated. In order to design robot that have smooth human like motion capability during human robot interaction in cooperative task, we need to understand how human-human understand each other, how and what kind of information was exchanged between them that enable human-human to be able to accomplish to move object with smooth qualities. Based on this, we need to design a system that is available to be used not only by robotic experts but by general population so that anybody can use this system for their care giving purpose. In this paper we conduct a study of how human-human utilize their sense in moving an object by utilizing a visual aid and we analyzed the smoothness of the motion by analyzing the hand jerk characteristic during the said task.

Control systems for cooperative robots should be designed to work imitating human characteristics. So it is important to know the human characteristics in a cooperative task, i.e. carrying an object by two humans. In this study, we have tried to achieve these goals by means of controlling a simple one degree-of-freedom cooperative robot. Firstly, the control characteristics of two humans in the cooperative task are investigated. Then, the cooperative task is modelled and the parameters of the model are evaluated. Finally, the proposed model is implemented to control a robot in order to perform a cooperative task with humans. It is observed that the proposed control methodology has given human like movements to the robot for cooperating with a human.

Robots are expected to be human-friendly and to execute tasks in cooperation with humans. Control systems for such robots should be designed in order to adapt human characteristics. In this paper, a variable impedance control method for robot to cooperate with human is proposed. First, the human characteristics in a cooperative task between two humans are analyzed. It is confirmed that human characteristics can be expressed by a variable impedance model. Then, we make a robot and a human to execute a cooperative task. It is shown that the impedance parameters obtained in the experiment performed by two humans give the best characteristics to the robot for cooperation with the human.

This paper considers the generation of skillful control actions, which require high experience of a task, by manual control using a master-slave manipulator. The authors have shown that a robot manipulator can be "taught" a skilled task using a "teaching method" based on manual control at a master manipulator. It takes, however, a long time for a human operator to control the master-slave manipulator satisfactorily when the task is complicated. In this paper, an iterative modification method using the master-slave manipulator (IMMSM) is proposed, which makes it possible to improve the movement of the slave based on performance evaluation. As the master-slave manipulator is usually used in teleoperation, the master is complicated and expensive because of the high maneuverability required. By applying the proposed method, a simple device like a joystick can be used. Using a joystick and a small manipulator, the authors have investigated the effect of IMMSM allowing iteration in the "teaching" of a simple task. The experimental results show that the operator can "teach" a skilled task to the robot manipulator using IMMSM. The oscillation frequency of the task error becomes large as progress is made through iterative modifications and the operator, finally, can not modify the high frequency signal any further. To avoid this confusing development for the operator the high frequency signal of the master manipulator is restricted by a function like a low-pass filter. In an experiment, it is confirmed that a filtering function helps the human operator to perform IMMSM more accurately.>