Naoto Mizutani

Fuel consumption in a driving test cycle by robotic driver considering system dynamics

In vehicle performance tests, fuel consumption, the components of exhaust gas, and mileage are measured on a chassis dynamometer that simulates the road load. It is difficult even for a professional driver to maintain speeds within the tolerance band of driving test cycles. Thus, there has long been an expectation that robotic drivers will be able to test vehicle performance with high reproducibility. In previous studies of robotic drivers, the improvement of tracking performance has been studied for each driving test cycle. In this study, we proposed a control system for realizing a driving test with smooth pedal use and low fuel consumption. We derived a set reference speed profile within a tolerance band from a driving test cycle standard. First, we performed a vehicle pre-test with a professional driver. From this driving test, we found that the square value of the power consumed by the vehicle was effective for driving with smooth pedal operation. Therefore, we proposed an objective function considering the square value of the power. We then derived the reference speed in a driving test cycle tolerance band for the robotic driver by the proposed method. Finally, we performed the vehicle test using the robotic driver. In the test, we used a standard JC08 chassis dynamometer, a moving averaged JC08 waveform, and the proposed speed waveform. We made sure that the proposed system was effective using the results of the actual vehicle tests.

A wheelchair operation assistance control for a wearable robot using the user's residual function

Cervical Cord Injury (CCI) is a dysfunction of the upper limb. In an individual with C5-level CCI, which is the most frequent of all eight levels, force can be applied in the direction of flexion by the biceps brachii, but extension force cannot be applied because of the triceps brachii paralysis. Persons with C5-level CCI therefore cannot operate a wheelchair up an incline and over carpet. In this study, we estimated the wheelchair velocity during elbow flexion depending on the angular velocity of the elbow. A wearable assistive robot can assist with the elbow extension movement using this estimated velocity while the wheelchair is being operated.

Extension Force Control Considering Contact with an Object Using a Wearable Robot for an Upper Limb

Thousands of individuals of all ages are living with a spinal cord injury as a consequence of a traffic, or sports accident or other calamity, and many of these individuals incurred a C5-level spinal cord injury, with a loss of the ability to use their legs and exert extension force from the elbow joints. Many of the motions that are necessary in daily life are difficult or impossible to perform with this level of spinal cord injury, and it is expected that wearable motion-assist robots will someday be available for use by individuals with C5 injuries. In order to be wearable, an assist robot must not limit the users range of motion while being used, and it must be suitable for a wide range of situations. In the present study, we developed an extension force support system that acts in accord with the operators intentions under the effect of external force as the operator use a wearable motion-assist robot for an upper limb. The effectiveness of the developed system was demonstrated experimentally.

Elbow joint motion support for C4 level cervical cord injury patient using an exoskeleton robot

We previously proposed a motion support robot and conducted experiments in which a C5-level cervical cord injury patient used the system. This paper proposes to offer motion support to a C4-level spinal cord injury patient who suffers from paralysis of the limbs. Electromyogram (EMG) signals are used to determine the users intentions. The proposed motion assist robot can then support flexion and extension at the elbow joint. Using frequency analysis of the EMG signal, the patients intention can be estimated in real time, and the coefficient of viscosity is varied in an admittance controller. With the proposed motion assist method, we were able to realize arbitrary upper limb motion of a C4-level cervical cord injury patient.

Control of wearable motion assist robot for upper limb based on the equilibrium position estimation

In this paper, we propose a robotic system for assisting patients who have upper limb dysfunction in performing reaching movements through flexion. Since upper limb motion is more strongly needed than lower limb mobility for near work, a patients level of recovery of upper limb function influences daily life. Recently, with the widespread application of robotic technology in rehabilitation medicine, active movement has often been noted to be more important than passive movement for rapid recovery. A novel control method for assisting upper limb movement by using a control system with two degrees of freedom is proposed. In the process of estimating the trajectory, the minimum jerk criterion is used to compute the velocity trajectory and to determine the reach position. The aim is to eventually develop a movement assistance system for the upper limb which will enable wearers to perform flexion and extension covering ranges of motion which are otherwise impossible to achieve autonomously. The effectiveness of the developed system is demonstrated experimentally.

Driving force assistance control for wheelchair operation using an exoskeletal robot

Cervical Cord Injury(CCI) causes a form of upper limb dysfunction. In an individual with C5-level CCI, which is the most frequent of all eight types of CCI, force can be applied in the direction of flexion by the biceps brachii, while extension force cannot be applied by the triceps brachii. Without the ability of the triceps brachii to exert this force, individuals with a C5-level CCI cannot propel a wheelchair along a carpet or sloping road. In this study, we developed a driving force assistance control system for wheelchair operation using an exoskeletal robot. We first analyzed the difference between the wheelchair operations of a healthy person and a C5-level CCI. We then designed a control model that included a user and a wheelchair. The wearers arm was modeled as a two-link manipulator, and the extension force and hand position were estimated using the equation of motion. The estimated extension force was compared with the driving force required to operate a wheelchair with the target velocity defined at the time of flexion of an arm. We then applied the proposed method via an exoskeletal robot. The effectiveness of the proposed method is demonstrated by experimental of wheelchair operation with C5-level CCI.

Automatic driving control by robotic driver considering the lack of a driving force at changing gears

Vehicle performance tests are conducted to evaluate factors of vehicle performance such as fuel consumption and durability. Robotic drivers are often used in these tests to ensure that performance evaluate is reproducible, and various types of vehicles have been tested. Manual transmission (MT) vehicles are widely used and represent about 50% of vehicles in the world. When the driver selects the gear ratio in MT, speed control performance is degraded during changing the gear. Because a torque transmission between the engine and wheels is cut during this sequence, the driver must drive the vehicle while considering the influence of changing the gear. Therefore, control performance in MTs depends on drivers technique. If robotic drivers are used with MT, there is a possibility that performance will be significantly degraded because the robot cannot adjust to change the gear while driving. In this paper, we realized the driving while considering shift changes by the robotic driver. First, we modeled the lack of a driving force using the dynamic characteristics of the vehicle and the deceleration during changing the gear. We then derived a target vehicle speed waveform using the lack of a driving force model. Finally, we performed vehicle tests using a robotic driver. We confirmed the effectiveness of the proposed system from the results of actual vehicle tests.

Vehicle speed control by a robotic driver considering time delay and parametric variations

Robotic drivers are used in vehicle performance tests such as fuel consumption. The test vehicle is driven on the dynamometer for driving test cycles with defined time and speed. To compare fuel consumption of various vehicles appropriately, better control performance is necessary to maintain the target vehicle speed. However, it is difficult to realize better control performance because a vehicle is a controlled system with a dead time and a large model error. In this paper, we designed a control system that realizes better control performance for the controlled system with a dead time and a large model error. First, we built the driver model from vehicle characteristics. We then designed a control system that permits the modeling error. The speed control performance of the proposed control system was confirmed by vehicle running tests with robotic driver.

A novel haptic display based on curvature estimation and its application to a machining support robot

For finish processing of limited-production diversified products of complex shapes, the use of a bilaterally controlled robot is in some sense inevitable. However, a bilateral control system is very difficult to operate because a worker must be in constant contact with the slave tool. So, in this paper, we propose a method to show the shape of the workpiece from the estimated curvatures of its parts. In addition, we have built a support system for processing that is specifically adapted to the proposed method. The system consists of a 6-DOF parallel haptic device as the master robot and 4-DOF parallel robot as the slave robot. The effectiveness of the proposed method is demonstrated through three different experiments.