Comparing uav remote sensing satellites and manned aircraft platform, has the characteristics of low cost, high flexibility.In order to satisfy the science remote sensing experiment, remote sensing work task, coordination of unmanned aerial vehicle (uav) multiple components in electronic pod working posture, control, remote sensing image sensor,System AT89S52 as the main control chip, expand multi-channel serial and USB interface so as to realize the communication system and peripheral equipment, and design the camera driver module and three dof stepping motor driver module.Through the uav remote sensing experiment proves that the system can satisfy the requirement of remote sensing experiment.
USB extension circuit design
USB extension by CH375 chip implementation.The general interface chip CH375 is the USB bus.Its main characteristic is cheap, convenient interface and high reliability.Support USB - HOST HOST way and way of USB DEVICE/SLAVE DEVICE.CH375 commonly used way of USB host support USB device at full speed, the external need to write the firmware program MCU in accordance with the relevant USB protocol and USB communication.But for common USB Storage devices, CH375 built-in firmware can automatic processing Mass - Storage Mass Storage equipment dedicated communication protocols,Normally, the external microcontroller don't need to write the firmware program. Can directly read and write data from USB storage devices.CH375 and MCU communication there are two ways: parallel and serial mode.USB extension circuit principle diagram as shown in figure 3, CH375 chip set to the built-in firmware mode, use 12 MHz crystal.SCM P0 port connected with the CH375 D0 ~ D7 as a data bus, decoder output connected pieces selected the chip CH375, microcontroller A0 and CH375 A0 is linked together, the choice of CH375 address and data input and output.When A0 to high level is the address of the transmission is D0 ~ D7, low electricity at ordinary times is the data transmission.P3.6 and P3.7 control of CH375 to read and write operation respectively.MCU input CH375, when there are data input through the USB port the interrupt signal, notify the single-chip computer for data processing.When CH375 chip initialization and successfully connected with the master, indicator.
Stepper motor drive circuit
Stable yuntai control three degrees of freedom for stepper motor control, the control of the remote sensing sensor pitch Angle, roll Angle and course Angle to keep stable yuntai horizontal (or vertical) state.Stepping motor driven by THB6128 chip implementation, microcontroller only output step motor running direction and the pulse signal can achieve the goal of control of stepping motor.
THB6128 is high subdivision, special chip two-phase hybrid stepping motor driver output control signal by single chip microcomputer, can design a high performance, multiple subdivision drive circuit.Its characteristics for both bridge MOSFET drive, low on resistance Ron Ω = 0.55, the highest 36 V voltage, large current 2.2 A (peak), A variety of optional segment, up to 128 segments, half with automatic locking function, fast, slow decline, optional hybrid three decay modes, built-in temperature protection and over-current protection.Figure 4 for the heading Angle of stepper motor drive circuit, pitch Angle and roll Angle of the stepper motor driver with the same.Figure in the CP1 and U/D of single chip microcomputer is given respectively drive pulse with the motor running direction of control signal.M1, M2, and M3 for motor drive fine points selection signal input, controlled by the dial the code switch artificially.FDT1 and VREG1 attenuation model respectively to choose voltage and current control voltage input end.When 3.5 V for slow attenuation model;When the attenuation model for mixed;When FDT1 "0.8 V for fast attenuation model. Adjust the voltage of the VREG1 can set stepper motor drive current value.
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