Steer-by-wire control method for underground load-haul-dump vehicles based on smooth inverse dead-zone compensation

The electrohydraulic steer-by-wire systems of underground load-haul-dump vehicles exhibit an input dead zone, causing delayed articulation-angle response and reduced tracking accuracy at low control-signal magnitudes. However, few studies have addressed dead-zone compensation in steer-by-wire control for these vehicles. To address these issues, a steer-by-wire control method for underground load-haul-dump vehicles based on smooth inverse dead-zone compensation was proposed. The actual articulation angle was measured using a single-turn absolute encoder, and the tracking error was calculated as the difference between the target and measured articulation angles. An incremental PID controller calculated a PID control signal from this error. A smooth inverse dead-zone compensation function then added a compensation term according to the direction and magnitude of this signal, generating the control signal for an electrohydraulic proportional directional valve. This valve drove differential extension and retraction of the steering cylinders, causing the front and rear vehicle bodies to rotate relative to each other about the articulation pin to achieve steering. Full-scale vehicle tests showed that smooth inverse dead-zone compensation reduced steering response time by 23.3% and total control-signal variation by approximately 38%. These results indicate that the compensation improves control smoothness while reducing response delay. The articulation-angle tracking error during the steady phase of step-trajectory tracking did not exceed 0.5°, and the maximum instantaneous error during sinusoidal-trajectory tracking was 4.9°, indicating high tracking accuracy for targets with different dynamic characteristics. Load had little effect on step-trajectory tracking accuracy. Although the peak sinusoidal-trajectory tracking error increased with load, tracking remained continuous and stable under heavy loads.