Robot-Assisted Adaptive Control Enhances Dental Drilling Force Stability

Tooth drilling is an essential dental procedure, but the varying mechanical properties of enamel and dentin make it difficult for robotic systems to maintain a constant drilling force. Fluctuations in force can increase the risk of tissue damage. This study compares four control strategies for position-controlled robotic arms to determine the best method for constant-force dental drilling under variable tooth hardness. A position-controlled arm with a six-axis force sensor was used for two experiments: (1) static tooth constant-force tracking and (2) dynamic tooth drilling. The target force was set at 5 N. The four control strategies tested were: Original Motion control (OM), TCP/CAN Direct-Drive control (TDDM), Natural Logarithm Function Extrapolation control (NLFE), and Force Adaptive Model-predictive Embedded control (FAME). Performance was measured using dynamic response indices (rise time, settling time, overshoot) and steady-state stability metrics (root mean square error, mean absolute error, peak-to-peak force fluctuation). All four strategies achieved basic force-tracking capability; however, their stability and disturbance resistance differed significantly. In static tests, FAME demonstrated the best stability with the smallest overshoot (13.28%) and the least difference between root mean square error and mean absolute error, indicating balanced force output. In dynamic drilling conditions with vibration disturbances, FAME achieved the shortest rise time (0.76 s) and maintained force within the predefined clinical tolerance range (5 ± 1.1 N) after convergence. In contrast, OM and NLFE had larger oscillations, while TDDM had frequent fluctuations. Overall, FAME showed the best stability, convergence, and resistance to disturbances in both static and dynamic tooth drilling. This approach enhances constant-force control under varying tooth hardness, making it a promising solution for safe and precise robotic dental procedures. FAME may improve force stability during robotic dental drilling, thereby reducing force fluctuation and supporting safer future clinical applications.