自律顎運動シミュレータJSN/2Bにおける開閉口および咀嚼様空口運動の制御(2部 運動特性)
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概要
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To clarify the control mechanism for jaw movements, we developed an autonomous jaw-movement simulator, JSN/1, consisting of upper and lower jaws, temporo-mandibular joint, muscular actuators, periodontal sensors, control unit, and a computer. The muscular actuator consists of a cable-tendon DC servo motor, equipped with a cable-tension sensor, and a rotary encoder capable of detecting cable length, thereby providing JSN/1 with masseter, temporalis, lateral pterygoid, and digastric artificial muscles. The actuators were controlled adaptively under an impedance-control mechanism, using bite force, and tooth contact data, plus the tension and length of the actuator cable. We also developed a physiological adaptive control scheme for open-close movement of JSN/1, using EMG data for related muscles. The previous simulator, however, had a defect: the temporalis actuators were activated under a non-physiological position control during closing in order to obtain high reproducibility of the movement. To eliminate that defect, we first incorporated artificial lateral ligaments into the temporomandibular joint of the simulator, in an attempt to provide the condylar movement with a passive restriction. Additionally, the drive signal for the anterior temporalis actuator was updated to cope with a delay of closing movement due to the reduction of the position-feedback gain. This update was accomplished not only by reducing the position-feedback gain, but also by dividing the signal into two different sinusoidal waveforms, each having a control parameter, thus enabling us to modify the signals for closing and biting phases independently. Accordingly, the drive signals for the masseter actuator and internal-pterygoid actuator, newly incorporated in the JSN/2B, were modified so as to be activated immediately after tooth contact. Their position-feedback gains were also reduced. The second aim of this study was to establish a simulator control scheme for chewing-like jaw movement without food, as a preliminary study for the simulation of actual chewing movement. We assumed that such movement can be obtained merely by modifying the values of several control parameters of the digastric, lateral-pterygoid, and posterior temporalis actuators, determined adaptively during open-close movement, and that the values of the parameters can be optimized using data relating to the amount of lateral shift of the mandible. Experiments using the updated JSN/2B verified that a lifelike, reproducible open-close movement could be obtained in the simulator even without high position-feedback in the actuator control, demonstrating both the necessity of joint ligaments for stability of condylar movement and the validity of our control scheme. In other experiments on chewing-like jaw movement, we introduced two different optimization functions to determine the values of the control parameters, using bite-force sensor data on the working side and tension sensor data for the lateral ligaments. Empirical results using both optimization functions demonstrated that a lifelike, reproducible chewing-like jaw movement could also be obtained by slightly modifying the values of the control parameters, which were first optimized during open-close movements.
- バイオメカニズム学会の論文
- 2002-06-00
バイオメカニズム学会 | 論文
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