Torque matching for an electric sliding door's drive system requires a systematic design based on the door's dynamic characteristics, integrating motor characteristics, transmission structure, and control strategy. The core principle is to ensure that the motor's output torque can both overcome the door's motion resistance and dynamically adapt to load fluctuations. Door motion resistance is a fundamental boundary condition for torque matching and includes additional resistance due to rolling friction, windage, inertia, and guide rail inclination. For example, during startup, a heavy-duty electric sliding door must overcome the instantaneous resistance of static friction and inertia. During high-speed operation, continuous torque must be provided to offset the combined forces of windage and rolling friction. The design should estimate the total resistance torque through experiments or empirical formulas, and include a safety factor to account for extreme operating conditions.
Motor selection should be based on load torque and speed requirements. Permanent magnet synchronous motors (PMSMs) are the mainstream choice for electric sliding doors due to their high efficiency, high power density, and wide speed range. Their torque output characteristics must match the door's motion profile. For example, during the door's startup phase, the motor must have instantaneous overload capacity to overcome static friction. During constant-speed operation, torque stability is required to reduce vibration. During deceleration, regenerative braking or mechanical braking is required to achieve a smooth stop. Furthermore, the motor's protection level must meet requirements for outdoor or humid environments, and its insulation performance must be suitable for long-term operation to ensure system reliability.
The design of the transmission structure is crucial to torque transmission efficiency. Common transmission methods include belt, gear, and chain drives, each with its own application scenarios. Belt drives offer low cost and low noise, but are prone to slippage and require a tensioning device to compensate. Gear drives offer high efficiency and precision, but are more expensive and require regular maintenance. Chain drives are suitable for heavy loads but exhibit significant noise and vibration. Electric sliding doors typically utilize either belt or gear drives. The appropriate transmission method must be selected based on door mass, operating speed, and environmental conditions. The transmission ratio must be optimized to achieve a balance between torque and speed. Excessively large transmission ratios may result in insufficient motor speed, while too small a ratio may lead to redundant motor torque, increasing energy consumption.
Control strategies play a key role in dynamically adjusting torque matching. Closed-loop vector control decouples torque and flux to precisely distribute stator current, thereby improving drive efficiency. Under constant thrust, the id=0 control strategy minimizes stator current and is particularly suitable for permanent magnet motors with a saliency ratio of 1. Furthermore, space vector pulse-width modulation technology optimizes voltage vector synthesis to reduce harmonic losses, further improving system energy efficiency. The control algorithm must integrate dual closed-loop position and speed control. The position loop serves as the outer loop to control door displacement, while the speed loop serves as the inner loop to control motor speed. Dynamic torque output adjustment ensures smooth door operation.
Dynamic load adaptation is a key challenge in torque matching design. During operation, electric sliding doors may encounter sudden changes in wind resistance, foreign objects in the guide rails, or human interference, resulting in instantaneous changes in load torque. The design requires real-time monitoring of motor output torque through a torque observer. Combined with the load model, torque demand can be predicted, allowing dynamic adjustment of control parameters to maintain system stability. For example, if a sudden increase in load torque is detected, the control algorithm can temporarily increase motor output torque to overcome the resistance, then restore the speed to the target speed through speed regulation to avoid stalling or overload caused by insufficient torque.
Environmental adaptability optimization can expand the application scenarios of electric sliding doors. In low-temperature environments, the increased viscosity of the motor lubricant can lead to increased transmission resistance, requiring friction reduction through preheating or the use of low-temperature lubricants. In humid or corrosive environments, IP65-rated or higher protection is required for the motor and stainless steel transmission components to prevent electrical failures and mechanical corrosion. Furthermore, outdoor electric sliding doors must consider the impact of wind loads. Reducing wind resistance torque by strengthening the door structure or adding windbreaks reduces the torque capacity required by the drive system.
