This paper describes a novel regenerative braking control scheme of electric power-assisted wheelchairs for safety driving on downhill roads. The ldquoelectric power-assisted wheelchairrdquo which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people; however, it has no braking system to suppress the wheelchair's velocity and brings the dangerous and fearful driving particularly on downhill roads. Therefore, this paper proposes a novel safety and efficient driving control scheme based on the regenerative braking system. This paper applies the regenerative braking system with the step-up chopper circuit serially connecting two motors and realizes the velocity feedback control with the variable duty ratio so that it tracks the optimal velocity based on the minimum Jerk model. In addition, the dynamic braking system is also applied at the low-speed range instead of the regenerative braking in order to suppress the acceleration. Some driving experiments on the practical downhill roads show the effectiveness of the proposed control system.

Novel Regenerative Braking Control of Electric Power-Assisted Wheelchair for Safety Downhill Road Driving

Red-green color difference has the good classification capability than that from individual components R, G, B or red-green ratio in RGB color space.Adaptive segmentation technique segments the unripe tomato images from the background with a good effect.Decision trees for automatic rule learning repudiate the need of a human expert.Automatic fuzzy partitioning of the feature space to over linguistic terms.High true positive rate and lower false positive rate for the proposed fuzzy rule base classification. High classification accuracy achieved by the proposed system over learning algorithms. Tomato (Solanum lycopersicum) ripeness estimation is an important process that affects its quality evaluation and marketing. However, the slow speed, subjectivity, time consumption associated with manual assessment has been forcing the agriculture industry to apply automation through robots. The vision system of harvesting robot is responsible for two-tasks. The first task is the recognition of object (tomato) and second is the classification of recognized objects (tomatoes). In this paper, Fuzzy Rule-Based Classification approach (FRBCS) has been proposed to estimate the ripeness of tomatoes based on color. The two color depictions: red-green color difference and red-green color ratio are derived from extracted RGB color information. These are then compared as a criterion for classification. Fuzzy partitioning of the feature space into linguistic variables is done by means of a learning algorithm. A rule set is automatically generated from the derived feature set using Decision Trees. Mamdani fuzzy inference system is adopted for building the fuzzy rule based classification system that classifies the tomatoes into six maturity stages. Dataset used for experiments has been created using the real images that were collected from a farm. 70% of the total images were used for training and 30% images of the total were used for testing the dataset respectively. Training dataset is divided into six classes representing the six different stages of tomato ripeness. Experimental results showed the system achieved the ripeness classification accuracy of 94.29% using proposed FRBCS.

Fuzzy classification of pre-harvest tomatoes for ripeness estimation - An approach based on automatic rule learning using decision tree

Physical and mechanical properties of tomato fruits as related to robot’s harvesting

A power assist wheel chair robot by which a patient can climb over a step up to about 10 cm without a helper is proposed in this paper. A patient can maintain inverse pendulum control of the wheel chair after raising its front wheels. Then, a patient can move to the step maintaining the inverse pendulum control, and can climb over the step using DC motor force. In this paper, the dynamics of the front wheel raising of the wheel chair, the mechanical designs, the control system, the experimental results of the front wheel raising and the inverse pendulum control are presented.

Front wheel raising and inverse pendulum control of power assist wheel chair robot

Wheelchairs on two wheels are becoming essential part of life for disabled persons. But designing control strategies for such wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics a double inverted pendulum with three actuators, one for each wheel, and one for chair position. The system starts to work with lifting the front wheels (casters) to the upright position and further with stabilizing in the upright position. The challenge resides in the design and implementation of suitable control strategies for the two-wheeled wheelchair so as to perform comparably similar to a normal four-wheeled wheelchair. A two-level modular fuzzy logic controller is proposed in this paper. A model of the standard wheelchair is also developed as a test and verification platform using Visual Nastran software integrated with Matlab.

A Modular Fuzzy Control Approach for Two-wheeled Wheelchair

A robot system to pick a tomatoes automatically using an easy-to-operate user interface is proposed in this paper A 3D-movement robotic arm with a hand system is used as the mechanical system The hand system is composed of a scissor device and a CCD camera The user can monitor the operation using the CCD camera linked to a personal computer, and can operate the robot system using only the user interface of a personal computer display It is possible to implement remote control operations using the proposed system The operational flow is as follows A user searches for a tomato using the velocity operation mode After the user has found the tomato on the display, he clicks on it The computer system recognizes the red color of the tomato, and then calculates the position of the tomato on the display Next, the calculated position moves to the center of the operation window The movement means that the robot hand moves to the corresponding position of the tomato Finally, the robot hand picks the tomato automatically The validity of the proposed robot system was confirmed by experimental results

Automatic tomato picking robot system with human interface using image processing

A biped robot technology for household use is proposed in this paper. The motivation of the biped robot is to assist an aged person with an unsteady walk in walking and moving up-and-down stairs. The robot has two legs with waist, and its waist is fixed to a handrail of a house using linear guides. The robot is able to walk by supporting itself on the handrail. A control bar is attached to the robot waist. An aged person can easily walk and move up-and-down stairs by stepping onto the feet of the robot. The robot structure using the handrail is advantageous since it allows for a compact, lightweight, and low cost robot mechanism. A scaled down biped robot was fabricated in order to confirm the proposed principle, and the simulation study was also carried out.

Biped robot to assist walking and moving up-and-down stairs

A tea serving robot for bedridden people is proposed in this paper. The tea serving robot is a standing-on-the-floor type with light weight, requiring a small installation area, and can be easily moved. A robot arm and hand can grasp a tea cup and carry it three dimensionally. A weak stiffness cantilever arm is used as the robot arm in order to ease bedridden people's tension. The bedridden person can easily catch and stop the robot arm and hand. The vibration reducing control of the robot arm is considered. The tea serving robot is actuated following the voice instruction. Therefore, the bedridden person can easily order the robot to carry a cup of tea.

Standing-on-floor type tea serving welfare robot using voice instruction system

Two man-machine interfaces of assist robots are proposed in this paper. By using the proposed man-machine interfaces, a person who has some difficulty in moving his/her arm can actuate assist robots with little finger force. Two types of assist robots, three-dimensional manipulators, were fabricated in order to confirm the proposed two man-machine interfaces. The first man-machine interface is composed of three strain gages, and a user of the robot pinches an operation plate to move the robot. Operation place is limited to actuate the robot; however, the robot can be moved smoothly in three-dimensions. The second man-machine interface uses an acceleration pickup. The second method is sensitive to noise. A user of the robot can actuate the robot by pushing or pulling at any point of the robot, operation place is not limited. The characteristics of the two methods are discussed through the experiments using the fabricated assist robots.

Y. Takahashi

Papers

Front wheel raising and inverse pendulum control of power assist wheel chair robot

Automatic tomato picking robot system with human interface using image processing

Biped robot to assist walking and moving up-and-down stairs

Standing-on-floor type tea serving welfare robot using voice instruction system

Man-machine interface of assist robot for aged person