Abstract: This paper proposes a low-cost PC-based eight-axis motion controller. The hardware consists of an 8-channel incremental encoder input signal processing circuit and an 8-channel 16-bit D/A conversion circuit. Motion trajectory planning and control strategies are designed as function libraries, which are called by the PC to complete the calculations. All circuits are installed on a 185mm×12-gram PC short card. Compared with the card using a dedicated motion control chip, this design not only reduces costs but also makes full use of the PC's computing resources, flexibly implementing various advanced control algorithms. This has important practical significance for constructing a low-cost open CNC system. Keywords: Motion control, PC, Open CNC system, Low-cost open CNC systems currently mostly adopt an industrial PC plus motion control card structure. In this structure, the PC usually completes trajectory planning, tool compensation calculation, interpolation calculation, etc., while the motion control card completes the control of servo motors or stepper motors. Most motion control cards sold on the market now use on-board dedicated motion control processors, which are often more expensive than the PC itself, and generally can only implement PID control. The primary reason for using on-board processors in motion controllers is the limitation of sampling time: within a limited sampling time, the CPU in a PC cannot simultaneously perform trajectory interpolation and servo control calculations. This was indeed the case in the past. However, with the increase in PC processing speed, this is no longer an issue. This paper proposes a motion control card that does not use an on-board processor. This card consists of an 8-channel incremental encoder input signal processing circuit and an 8-channel 16-bit D/A conversion circuit. Motion trajectory planning and control strategy calculations are performed by the PC. [Click for details]