The motion of a snowboarder is seemingly complex. In order to model that motion and its complexity, we have devised two snowboarding robots. One robotic model incorporates flexion and extension of the knee joint, while the other model integrates flexion and extension of the hip joint. These motions were accomplished through the attachment of a servomotor to the knee and hip joints, respectively. From a basic posture, the knee joint model - incorporating flexion and extension-leans toward and over the front side of the extended knee joint and leans toward and over the back side of the flexed knee joint. So, the knee joint model attains to a posture that rises toward and over, the front side and squats down toward and over the back side. From a basic posture, the hip joint model-incorporating flexion and extension - shows a lean toward and over the front side of the flexed hip joint, and it displays a lean toward and over the back side of the extended hip joint. The hip joint model then becomes the posture which bends the waist toward and over the front side and the posture which bends backward and over the back side. These postures are the inward-leaning postures performed duringa turn. It is this sort of motion which causes the snowboard to be edged. The edging of the snowboard shifts according to these motions. To make a front side turn, the robot extends the knee and/or flexes the hip; to make a back side turn, it flexes the knee and/or extends the hip. Using a side-cut snowboard enables the performance of a carving turn. Moreover, these models are capable as well of achieving a sequential turn. As it turns out, the width of the snowboard plays an important role in allowing the model to make stable, repeated turns.

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The turning motion of an alpine snow ski is made possible by centripetal force and the moment around the center of mass. Both the force and moment are produced by resistance forces from the surface of the snow. The centripetal forces are obtained by placing the ski's longitudinal axis at an angle inclined away from the velocity vector and simultaneously edging the ski into the snow. A experimental device rotates a compact snow specimen and cuts it using a cutting tool by simulating the edge of a ski. In order that it can be cut while rotating with the attack angle set up in the whole cutting tool, the circular-arc type cutting tool was developed and it used for the experimental device. The force sensor attached in the cutting tool measured three components of snow cutting force, i.e. a horizontal component inverse to the cutting direction, a vertical upward component to the snow surface, and a transverse component vertical to the cutting and vertical direction. The transverse component corresponds to the centripetal force which makes ski's turning motions possible. The result of an experiment showed the effects of cutting speed, attack angle, and edging angle on snow cutting forces. The snow cutting force equations were obtained by applying multiple regression analysis to experimental data.

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In order to clarify the mechanism of a turning ski, a skiing robot which controls parameters in respect of snow resistance force was developed. The turning motion of an alpine snow ski is made possible by centripetal force and the moment around the center of mass. Both the force and moment are produced by resistance forces from the surface of the snow. Various actuation of the skier on a turning ski results in controlling a snow resistance force. A robot with servo-motors controls snow resistance force by the actuation of an edging angle, back and front movement of a ski board, and centre-of-gravity movement. In order for a robot to turn autonomously, it is necessary to recognize the turning phase. The microcomputer and the gyro sensor are attached in a robot. A direction angle is calculated by integrating with the angular speed measured with the gyro sensor, and a robot recognizes the turning phase, judging from the continuity of a direction angle. The skiing robot performs skiing operation responding to the turning phase. The turning ski trucks of a skiing robot was measured by a digital video camera. And the effects of skiing operation on a ski truck was investigated using a skiing robot.

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