Precise trajectory control is the core technology for ensuring safety and stability when climbing stairs in a conventional electric stair climbing wheelchair. Its implementation relies on the coordinated work of mechanical structure, sensor system, control algorithm, and drive system. Through multimodal perception and intelligent decision-making, the wheelchair can adapt to the geometric features of different staircases, achieving a seamless transition from flat ground to steps. Its technical principle can be broken down into the following key aspects:
Mechanical structure is the foundation of trajectory control. Conventional electric stair climbing wheelchairs typically employ a tracked or star-wheel chassis design. The former disperses pressure through the contact between continuous tracks and the edge of the steps, while the latter relies on the combination of the revolution and rotation of multiple small wheels to achieve climbing. Taking the tracked type as an example, its track surface is designed with anti-slip patterns to increase friction with the steps. Simultaneously, the track width must match the step depth to prevent lateral slippage during ascent. The star-wheel type uses "Y"-shaped or "+"-shaped tie rods to connect multiple small wheels. When traveling on flat ground, the small wheels rotate; when climbing stairs, the tie rods drive the small wheels to revolve, forming a gear-like motion pattern that ensures each step is precisely placed on the step surface.
The sensor system is the "eye" of trajectory control. Conventional electric stair climbing wheelchairs are typically equipped with tilt sensors, distance sensors, and encoders to monitor the wheelchair's posture and position in real time. The tilt sensor, mounted on the chassis, detects the angle between the wheelchair and the horizontal plane. When the center of gravity deviates beyond a safe threshold during stair climbing, the system immediately adjusts the drive motor output to prevent tipping. The distance sensor is deployed at the end of the tracks or outriggers to measure the distance to the edge of the step, ensuring the wheelchair always moves along the preset path. The encoder, mounted on the motor shaft, accurately calculates the wheelchair's displacement through pulse counting, providing feedback signals to the control algorithm.
The control algorithm is the "brain" of trajectory control. Conventional electric stair climbing wheelchairs often employ a hybrid algorithm combining fuzzy control and PID control. Fuzzy control, by simulating human driving experience, transforms continuous values input from sensors (such as angle deviation and distance error) into discrete fuzzy linguistic variables (such as "positive large" and "negative small"), and then outputs control commands according to a preset rule base. For example, when the tilt sensor detects that the wheelchair's forward tilt angle is too large, the fuzzy controller will prioritize increasing the rear wheel drive torque while decreasing the front wheel torque to quickly restore balance. PID control is used for fine adjustment, eliminating steady-state errors through proportional, integral, and derivative steps to ensure the wheelchair moves accurately along a straight or curved trajectory. The drive system is the executor of trajectory control. Conventional electric stair climbing wheelchairs typically employ a dual-motor independent drive design, with the left and right tracks or wheel sets individually controllable in speed and steering. This design not only improves flexibility when climbing stairs but also enables on-the-spot turning through differential control, adapting to the operational needs of narrow stairwells. During the stair climbing process, the system dynamically adjusts the output torque of the motors on both sides based on trajectory deviations fed back by sensors. For example, when the left track is too close to the edge of the step, the left motor speed will be appropriately reduced while the right motor speed will be increased, allowing the wheelchair to return to the center position.
The human-computer interaction design further optimizes the trajectory control experience. The operating interface of a conventional electric stair climbing wheelchair is usually integrated into the armrests or seat armrests. Users can input the target floor or movement mode via buttons, joysticks, or a touchscreen. Some high-end models also support voice control or remote operation via a mobile app; users only need to say "upstairs" or "downstairs," and the system will automatically plan the optimal path. In addition, the wheelchair is equipped with an emergency stop button, which can immediately cut off power in case of emergencies to ensure user safety.
Safety redundancy design is the last line of defense for trajectory control. Conventional electric stair climbing wheelchairs typically employ a dual-battery power supply and dual-motor redundancy design. Even if one component fails, the other system can still maintain basic functions. For example, when the main motor shuts down due to overheating, the backup motor can automatically take over, ensuring the wheelchair continues to complete the current stair climbing action. Meanwhile, the wheelchair is also equipped with an anti-slip braking device. If an abnormal speed is detected during stair climbing, the system will immediately trigger the brakes to prevent the wheelchair from rolling down the stairs due to inertia.
From a practical application perspective, the trajectory control technology of the conventional electric stair climbing wheelchair already meets the needs of most homes and public places. Whether it's a straight staircase, a curved staircase, or a spiral staircase, the wheelchair can achieve centimeter-level positioning accuracy through the collaborative work of sensors and algorithms. This precise control
not only improves stair climbing efficiency but also significantly reduces the risk of use, providing the possibility of independent travel for people with mobility impairments. With continuous technological advancements, the trajectory control of the conventional electric stair climbing wheelchair will become more intelligent in the future. For example, it can use deep learning algorithms to predict changes in stair structure or link with smart home systems to achieve automatic navigation and obstacle avoidance, further expanding its application scenarios.
