Design of ATV-ATT Central Control System Based on DSP

In order to effectively deal with sudden and large-scale terrorist violence, the development of non-lethal anti-riot weapons has been increasingly valued by various countries. The development of an anti-riot weapon system with a highly maneuverable ATV as a weapon platform is of great significance to improving anti-terrorism combat capabilities, and the modern control system makes the entire weapon system more controllable and intelligent. Therefore, a design scheme of an ATV-ATT central control system based on DSP is proposed here. The design uses DSP TMS320F2812 as the control core, controls the pitch and rotation of the weapon device through the handle, and controls its movement, ranging, automatic aiming and firing mode setting through the key method. When the operator presses the shooting button, the weapon control system automatically forms a signal to allow firing according to the set conditions, and then the weapon is fired or released. At the same time, the system has self-test and storage detection functions. 1 System design scheme The function of the ATV-ATT central control system of the all-terrain anti-terrorism and anti-riot weapon system is mainly to complete a series of controls such as the movement, ranging, aiming, and firing of the weapon system. As shown in Figure 1, the system includes three modules: motion module, key module, and communication module.

1.1 Motion control module
In the control system, the pitch and rotation of the launcher are controlled by the joystick. The handle can be equivalent to two independent potentiometers. The analog voltage range is 0-3 V, which meets the acquisition voltage range of the A/D conversion module. After the A/D conversion of the DSP (TMS320F2812) and the PWM waveform generation of the event manager (EV), two PWM waveforms are output to control the speed of the stepper motor (90BYG3502), and the direction is controlled by outputting high and low level signals through the powerful IO port of the DSP. When the signal is high, the motor rotates clockwise, and when it is low, it rotates counterclockwise in the opposite direction. However, since the voltage amplitude of the output signal of the DSP is between 0 and 3.3 V, it cannot meet the signal amplitude range of the stepper motor driver (MSa-3H090M). Therefore, these 4 signals are transmitted to the motor driver after passing through the boost drive circuit to realize the control of the motor.
At the same time, the system also has an aiming function. The optical axis of the laser rangefinder is coaxial with that of the video imager. When the aiming point displayed on the screen of the video imager points to the target, pressing the ranging button can trigger the ranging signal of the laser rangefinder. The DSP calculates the displacement in two directions under the launch state according to the angle between the two vertical axes of the horizontal inclinometer and the horizontal plane in the current state through a specific algorithm. The DSP gives a motor drive signal to drive the motor and compares the reading of the inclinometer in real time. When the reading reaches the threshold allowed by the calculated value, it is considered that the aiming is completed and the launch can be carried out.
DSP TMS320F2812 is a low-power 32-bit fixed-point digital signal processor. In addition to the advantages of general DSP, it also uses high-performance static CMOS technology, the voltage is reduced from 5 V to 3.3 V, and the core voltage is reduced to 1.8 V, which reduces power consumption. The instruction execution speed is up to 150 MHz, and almost all instructions can be completed in a single cycle of 6.67 ns. The chip also has a large number of peripheral resources, such as A/D conversion, timer, various serial ports (synchronous and asynchronous), watchdog, CAN bus/PWM generator, digital IO pins, etc. Therefore, DSP TMS320F2812 is selected as the system controller.
1.2 Key module
Parameter control includes micro-key control and two types of firing mode key control. Pressing the ranging key can change the pulse frequency in the DSP, and the handle can be used to finely control the firing device. The firing mode key controls the corresponding parameters of the DSP, so that the weapon can be fired according to the established firing mode. The firing mechanism is controlled by a relay. In this design, a GTJ8-8A solid-state relay is used. The firing key provides a control signal to the relay through the general IO port of the DSP, and 48 V is used as the excitation voltage for ignition, thereby realizing the firing process.
1.3 Communication module
The TMS320F2812 device includes a serial communication interface SCI module. The SCI module has an asynchronous serial port consistent with the RS-232 standard, which allows TMS320F2812 to easily communicate data with other asynchronous peripherals using standard formats. In this design, the communication subsystem completes the data communication control between the DSP and the horizontal inclinometer, laser rangefinder and video imager through the standard RS-232 serial port.

2 System Hardware Design
Figure 2 is the principle block diagram of the system design, which mainly gives the design of the boost drive circuit and the power supply circuit.

The boost drive circuit adopts the basic principle of the transistor amplifier circuit: the collector current is controlled by the base current, and a small change in the base current will cause a large change in the collector current, and the change satisfies a certain proportional relationship. Here, an NPN silicon transistor is selected to boost the two 3.3 V direction signals and two pulse signals output from the DSP to 5 V respectively, thereby driving the motor driver, as shown in Figure 3.

The power supply is the energy center of the entire system, and the performance of the system power supply circuit greatly affects the stability of the DSP system. The DC power supply input is a 48V vehicle battery, and the SPD75-XXS12 wide voltage constant current regulated power supply module is used to convert the 48V voltage into a constant 12V DC voltage, which in turn powers the central control board, horizontal inclinometer, laser rangefinder, etc.

The central control board has a 12 V DC input, which is converted to a +5 V DC power supply using 12S05. In addition to +5 V, the working power supplies of the internal components also include digital +3.3 V, analog +3.3 V, and digital +1.8 V. For this reason, a power supply module inside the central control board is specially designed to convert the +5 V voltage into several voltages required for the operation of each component. Two LM1117s are used here to convert +5 V into output voltages of +3.3 V and +1.8 V respectively. In order to avoid noise interference from the digital power supply to the analog power supply, the two are isolated by inductance, as shown in Figure 4.

3 System software design
The control system software is written in C language. The software mainly consists of the main program, serial port interrupt subroutine and A/D conversion interrupt subroutine. The main program is used for the initialization of the TMS320F2812 DSP, the conversion and input of control instructions and parameters, and the generation of stepper motor drive signals. The serial port interrupt subroutine is used to receive information from the horizontal inclinometer and laser rangefinder and send control instructions to them. The A/D conversion interrupt subroutine is used to receive the voltage change fed back by the handle potentiometer and convert it into a numerical value. The software execution flow is shown in Figure 5.

4 System debugging results
Solder the components on the circuit board, check whether there are any solder joints with false solder joints, measure whether there is any welding short circuit in the power supply, ensure that the power supply of the board is normal, and the connection between each module is correct, as shown in Figure 6.

Figure 7 shows the system connection diagram after the program is burned. After debugging, the program runs well, and the weapon system can realize 90° rotation movement, high and low direction movement within 60°, and control its micro-motion, laser ranging, automatic aiming and firing mode setting, self-test and stored bullet detection through key control and other functional requirements.

5 Conclusion
This paper describes the design of a certain ATV-ATT vehicle-mounted weapon control system. According to the different system functions, each module circuit is introduced separately. According to the basic principles of hardware design, suitable devices and reference circuits are selected, and then the hardware circuit is analyzed and designed, and the problems of boost drive and power supply are solved. Finally, through debugging and installation, the actual operation of the system verifies that the design is stable and achieves the application goal.