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A split belt treadmill for gait rehabilitation was developed to improve the symmetry of the stance phase time of patients with stroke. The system, which increases the stance phase time of the affected leg and then realizes a well-balanced gait, is divided into two components. First, the stance phases of the sound and affected legs were measured and presented visually in real time to the patient and physical therapist as biofeedback. Second, using stance phase biofeedback, the physical therapist sets two different velocities of treadmill belts for sound and affected legs. In an experiment, 11 patients with chronic stroke participated in a short-term intervention trial (20 gait cycles) of the developed treadmill system. Three of the five subjects who had lost balance between the stance phase of the sound leg and that of the affected one improved their gait balance in the intervention trial. In addition, one subject kept the well-balanced gait after the intervention.

We have been developing a robotic split-belt treadmill with different belt velocities and visual biofeedback of stance phase for the stroke patients to improve the symmetricity of their gait balance. In this treadmill system, a visual bio-feedback system of stance phase time of affected and unaffected legs is used. In this paper, a signal processing to eliminate spike and high frequency noises and oscillation of judge result of gait phase is discussed to indicate the stance phase time in real-time accurately. In addition, the effect of visual biofeedback of gait balance on their gait was analyzed in the determined biofeedback condition. Firstly, we conducted the gait experiment to determine the parameters in the signal processing such as cut-off frequency of low pass filter. In this experiment, the number of false judgment was calculated in normal gait, high cadence gait and simulated stroke gait. As a result, two parameters, cut-off frequency and the number of data to judge the gait phase, are set as 3.0 [Hz] and 10 respectively. In this condition, the gait phase of affected and unaffected legs are accurately displayed in front of stroke patient and physical therapist. Secondly, simulated stroke patients evaluated the effect of biofeedback of stance phase on the stance phase balance. As a result, the stance phase balance between affected and unaffected legs' stance phase was symmetrized by using visual biofeedback system.

We have been developing a new mobility device, Tread-Walk 2, which supports walk for elderly people. This paper describes a mechanical model which considers friction forces of the treadmill to improve the operability of Tread-Walk 2. As a first step, an anteroposterior force is estimated using motor current value. By comparing the estimated anteroposterior force using motor current value with the measured one using force plate, the waveform pattern of the estimated anteroposterior force was similar with that of the measured anteroposterior force in two young subjects whose physical characteristics were quite different.

A split belt treadmill robot for gait rehabilitation was developed to improve the symmetry of the stance phase time of patients with stroke. The system, which increases the stance phase time of the affected leg and then realizes a well-balanced gait, is divided into two components. First, the stance phase of the unaffected (“sound”) and affected legs is measured and presented visually in real time to the patient and physical therapist as biofeedback. Second, using the biofeedback of the stance phase, the physical therapist sets two different velocities of the treadmill belts for the sound and affected legs. In an experiment, eleven patients with chronic stroke participated in a short-term intervention trial (twenty gait cycles) of the developed treadmill system. Three of the five subjects who had lost balance between the stance phase of the sound leg and that of the affected one improved their gait balance in the intervention trial. In addition, one subject kept the well-balanced gait after the intervention. In the future, the algorithm to automatically adjust the belt velocities of the affected and sound sides and better biofeedback system with the sound leg information will be developed.

We have developed a gait rehabilitation robot for hemiplegic patients using the treadmill. A walk phase, which includes time balance of stance and swing legs, is one of the most basic indexes to evaluate patients’ gait. In addition, the walking phase is one of the indexes to control our robotic rehabilitation system. However, conventional methods to measure the walk phase require another system such as the foot switch and force plate. In this paper, an original algorithm to estimate the walk phase of a person on a treadmill using only the current value of DC motor to control the treadmill velocity is proposed. This algorithm was verified by experiments on five healthy subjects, and the walk phase of four subjects could be estimated in 0.2 (s) errors. However, the algorithm had erroneously identified a period of time in the stance phase as swing phase time when little body weight loaded on the subject’s leg. Because a period of time with little body weight to affected leg is often observed in a hemiplegic walk, the proposed algorithm might fail to properly estimate the walk phase of hemiplegic patients. However, this algorithm could be used to estimate the time when body weight is loaded on patient legs, and thus could be used as a new quantitative evaluation index.

The importance on walking for health is growing in elder dominated society. We have been developing a new mobility "Tread-Walk 1 (TW-1)" controlled by walking movement. The device uses active treadmill velocity control, which allows the user to walk on the treadmill at any desired velocity. In this paper, the walking movements on the TW-1 were kinematically analyzed and compared with the walking movements on a traditional constant-velocity treadmill and on flat ground. The results showed that the walking pattern on the TW-1 was somewhat similar to that on a constant-velocity treadmill and on flat ground; however, the flexion angle of the hip joint and the dorsiflexion and plantaflexion angles of the ankle joint during TW-1 walking were larger. It also was shown that the foot applied a stronger kicking force to the belt at toe-off and the foot clearance on the TW-1 was larger than that on the constant-velocity treadmill and on flat ground. Therefore, the walking patterns in the swing and stance phase on the TW-1 are little different. However, the walking movements based on the TW-1 active belt control are valuable from the viewpoints of motion training.

The importance on walking for health is growing in elder dominated society. We have been developing a new mobility “Tread-Walk 1 (TW-1)” controlled by walking movement. The device uses active treadmill velocity control, which allows the user to walk on the treadmill at any desired velocity. In this paper, the walking movements on the TW-1 were kinematically analyzed and compared with the walking movements on a traditional constant-velocity treadmill and on flat ground. The results showed that the walking pattern on the TW-1 was somewhat similar to that on a constant-velocity treadmill and on flat ground; however, the flexion angle of the hip joint and the dorsiflexion and plantaflexion angles of the ankle joint during TW-1 walking were larger. It also was shown that the foot applied a stronger kicking force to the belt at toe-off and the foot clearance on the TW-1 was larger than that on the constant-velocity treadmill and on flat ground. Therefore, the walking patterns in the swing and stance phase on the TW-1 are little different. However, the walking movements based on the TW-1 active belt control are valuable from the viewpoints of motion training.

An active body weight support (BWS) system, which unloads body weight with pelvic support, has been developed to assist the walking movement. This system unloads body weight with a motor-actuated device from below with pelvic support, unlike prevailing BWS systems that lift up the subject from above via a harness connected to a wire. The force control method to unload body weight has not been sufficiently studied. As a first step, a comparison study between normal walking and walking with the developed BWS mechanism was conducted to specify the force control method. Since the precise and constant unloading force is believed to be an important prerequisite for BWS gait therapy, different constant unloading forces were set as the target unloading force. The target unloading force was varied from 100 (N) to 300 (N) to observe the difference among forces. The measured unloading forces were not completely constant but fluctuated. The motor introduced a delay at over 200 (N) during lifting. As a result, the floor reaction force was reduced by the target unloading force. However, some differences were found in the bimodal shape of the floor reaction force and the trajectory of the sacrum's vertical position. The results showed the necessity of damping the fluctuation of unloading force by improving following characteristics and adjusting target velocity. Further precise force control will be carried out to realize constant unloading force.

We have been developing a new vehicle, “Tread-Walk 2”, which supports walking for elderly. A control algorithm to improve the operability has been constructed. As the first step, we accurately estimated the user's anteroposterior force from the motor current value without the force sensor. This method is to develop a new mechanical model that considers the friction forces of the treadmill and remove the modeled friction losses from the output. However, we need the vertical force in order to develop a mechanical model. Thus, we proposed the new method to estimate the vertical force without the force sensor. This paper describes the new method to approximate the waveforms of the vertical forces as square waves by adding the user's weight as a parameter to the stance phase. By comparing the estimated anteroposterior force using the new method with the measured one using the force plate, the waveform pattern of the estimated one was similar with that of the measured one in two young subjects whose physical characteristics were different. This showed that the proposed method might possibly be useful for estimating the anteroposterior force in real-time.