I. Introduction AC servo systems have been widely used in mechanical manufacturing, industrial robotics, aerospace, and other fields. To achieve better dynamic and static performance, most of the controlled objects utilize permanent magnet synchronous motors (PMSMs). Direct torque control (DTC) is a new type of variable frequency speed control technology that emerged in the AC speed regulation field after vector transformation control. This technology abandons the decoupling concept of vector control, replacing rotor field orientation with stator field orientation, reducing the system's dependence on motor parameters. It does not require complex coordinate transformations like vector control, resulting in a simpler system control structure, faster torque response, and enhanced robustness. This paper introduces a high-performance, fully digital AC servo control system employing DTC. 2. In the direct torque control principle of AC servo systems, when controlling permanent magnet synchronous motors (PMSMs), if the stator resistance is ignored and the stator-rotor flux linkage angle is taken as the load angle, the electromagnetic torque of the motor is as follows: When performing direct torque control on a PMSM, the stator magnetic field amplitude (the magnetic field generated by the permanent magnets on the rotor) is usually kept constant. The electromagnetic torque is controlled by changing the rotational speed of the stator flux linkage and the flux linkage angle to achieve speed control. The model of the stator flux linkage and electromagnetic torque of a PMSM in a stationary two-phase coordinate system (a=3) is as follows: Based on the above formulas and references, the block diagram of the direct torque control system of the PMSM is shown in Figure 1. In Figure 1, S is the position control signal, sT is the position regulator. Considering the uncertainty and variability of the mathematical model of the controlled object, sT adopts a fuzzy parameter self-correcting controller, and ASR is the speed regulator (Pl regulator). ATR and AFR perform discrete two-point regulation on the torque signal i and the stator magnetic field signal respectively to obtain control signals r and q. Then, the stator voltage vector of the motor is determined by looking up a table based on the position of the stator flux linkage. In this scheme, the motor torque feedback signal and stator magnetic field feedback signal are obtained by parameter identification calculation of stator voltage and current. [b]3. Hardware Circuit Design of the System[/b] Based on the system's principle block diagram, the hardware circuit of the AC servo control system is designed as shown in Figure 2. It mainly includes three parts: main circuit, control circuit, and protection circuit. (1) Main Circuit The main circuit uses the P22X intelligent power module produced by SIEMES. This module is a highly integrated rectifier module, inverter module and various sensors and drive protection circuits. Its main characteristics are as follows: ① Recommended load is 147kW; ② Rated input voltage of the module is 230V (AC); ③ Typical switching frequency is 20kHz; ④ Protection functions are undervoltage, overcurrent and overheat, and output fault signal when fault occurs; ⑤ The module integrates a 220~ rectifier module; ⑥ Power factor correction (PFC) circuit is integrated; ⑦ The IGBTs of the upper and lower bridge arms inside the module have a dead time of 2"s; ⑧ Other various detection and protection functions. (2) Control Circuit In order to realize the direct torque control of the system and the complete detection and protection functions in real time, the control circuit is designed with the 80C196 microcontroller as the core, which constitutes a fully functional real-time control system. The two microcontrollers communicate in parallel through dual-port RAM. The main components in the control circuit perform the following tasks: 1) Microcontroller #1, model INTEL80C196KC, primarily performs tasks such as position loop control and system monitoring. Its main functions include: receiving control signals from the serial 121 input and motor position signals from the photoelectric encoder; implementing the fuzzy adaptive control algorithm for the position loop to obtain the speed command signal; sending the speed command signal to microcontroller #2 via parallel communication through dual 121 RAMs; receiving and processing keyboard input signals; outputting system display signals to the monitor; and performing system fault detection. 2) Microcontroller #2, model INTEL80C196KC, was chosen primarily because its output signals control the inverter. The INTEL80C196KC is a microcontroller specifically designed for motor control, containing an internal PWM drive signal generator called WG, which consumes very little CPU time. Six SPWM signals are directly output from port P6 for driving the P22X. The drive current per ten pins can reach 20mA, and the drive frequency is also very high. The dead time can be set by the program to prevent two IGBTs on the same bridge from passing through. The #2 microcontroller mainly performs the following tasks: Receives speed command signals from dual 121 RAMs; performs AID conversion on voltage and current signals; performs speed loop, torque loop, and flux loop calculations; looks up the voltage switch vector table; generates PWM drive signals from WG to complete overcurrent, overvoltage, and other fault detection and protection functions. 3) Dual-port communication: Parallel data communication between the two microcontrollers uses dual-port RAM IDTT130, a high-speed IK x The 8K dual-port static RAM, with on-chip bus arbitration circuit, is suitable for fast bidirectional transmission of large amounts of data between two machines. The IDTT130 provides two independent control and address buses, and also provides two bus arbitration modes: BUSY and INT. All MCS96 series chips have Ready pins. Connecting them to the BUSY pin of the IDT7130 can achieve delay. The integrated competition logic inside the IDTTI30 chip is based on the principle of priority for the first-to-last access signal. When the left and right CPU access ports are accessing addresses or matching chip selects at the same time, the BUSY pin of the slower access port will be pulled down to invalidate the write operation. Once the other access is completed, the BUSY line of the slower access port will be restored to the pull-up level, and the dual-port RAM can continue to be accessed. (3) Protection function and drive circuit The intelligent power module P22X is equipped with fault signals such as overvoltage, overcurrent and overheat. These signals are sent to the EXTINT terminal of the 80C196MC through opto-isolation. As long as any one of them plays a protective role, the output of the WG waveform generator will be blocked immediately, and the three-phase PWM wave generation will be prohibited, thus improving the reliability of operation. Simultaneously, the fault code is stored in the EPROM and displayed on the monitor for maintenance. The drive circuit uses a dedicated integrated chip EXB840, which can achieve optimal IGBT drive. The EXB840 has internal circuits for overcurrent detection and slow overcurrent cutoff. When the IGBT experiences severe overcurrent or shoot-through between the upper and lower bridge arms, its collector voltage rises. The EXB840 shuts down the IGBT at a slower speed to avoid damaging it and requests a switch from the microcontroller. [b]4. Software Design[/b] The control system software mainly consists of two parts: the software for microcontroller #1 and the software for microcontroller #2. The software structure of microcontroller #1 is shown in Figure 3. The main program of microcontroller #1 mainly completes tasks such as system initialization, parameter setting, and system monitoring. {The position loop control is implemented by a software timer interrupt service routine. The software timer interrupts once every 1ms to complete position detection, the fuzzy adaptive control algorithm of the position loop, and obtain the motor speed command signal.} The control program flowchart for the position loop is shown in Figure 4.2. The microcontroller program mainly performs the following: initialization, system monitoring, current and voltage sampling and A/D conversion, speed calculation, reading and writing dual 121 RAM, motor model parameter identification and calculation, running the speed loop program, running the ATR and AFR discrete two-point control algorithms, and checking the voltage vector table to control the WG output PWM signal. Additionally, in case of a fault, the fault interrupt program handles the fault signal, records the fault type for display and query, and transmits the fault type to microcontroller #1. 5. Introduction Experimental results show that the AC servo control system using direct torque control has extremely high steady-state control accuracy, fast dynamic response, and strong anti-interference ability. The algorithm is relatively simple after adopting direct torque control, and the system robustness is enhanced. Furthermore, the use of dual 121 RAM IDT/130 solves the problem of fast bidirectional data transmission between the two keys, with high reliability and good potential for widespread application. Click here to download the original text.