CN112783162A - Intelligent shopping system - Google Patents

Abstract

The invention provides an automatic following shopping system which liberates both hands of a user, improves the shopping experience of the user as a background and can change the speed along with the change of the weight of a carried object, and the automatic following shopping system comprises a processor module, a power supply module, a driving module, a target detection module, a pressure detection module, a distance measurement module and a human-computer interaction module; the invention is based on the angle of users and shoppers, solves the problem of heavy burden caused by the distance from the home to the shopping supermarket and the shopping mall of the users, and the traditional automatic following shopping system comprises the modes of infrared guide following, sonar guide following, indoor positioning, camera identification environment and the like.

Description

Intelligent shopping system

Technical Field

The invention relates to the field of electronic information, in particular to an intelligent shopping system.

Background

With the development of internet technology, the development of entity sales enterprises is more difficult due to the impact of online transaction marketing modes, and consumers are urgently attracted by providing better shopping environments and better shopping experiences. Heavy goods can increase physical burdens on customers when shopping more, resulting in a reduced level of consumer experience for the customer. The automatic following shopping system is designed to solve the problems and liberate the hands of the user, so that the pleasure brought by shopping is improved.

The automatic following shopping system is a product of research of a wheeled mobile robot, and an autonomous following mobile technology is one of core technologies of the automatic following shopping system. The research on the automatic following movement technology is continuously being strengthened due to the complicated environment in which the automatic following shopping system is applied. In addition, the current automatic following shopping system mainly carries out research design by taking a large supermarket as a main body, has no specific design for the application scene specific to the user, cannot bring great convenience to the user, and cannot realize good marketization of products.

The invention is based on the angle of users and shoppers, and mainly solves the problem of heavy burden caused by the distance from home to shopping supermarkets and shopping malls of the users.

Technical problem

In order to solve the problems that a shopping system in the prior art does not carry out targeted design on a specific application scene of a user, cannot bring great convenience to the user and cannot bring good marketization to products, the invention provides an automatic following shopping system which liberates both hands of the user, improves the shopping experience of the user as a background and can change speed along with the change of the weight of a carried object, and the automatic following shopping system comprises a processor module, a power supply module, a driving module, a target detection module, a pressure detection module, a distance measurement module and a human-computer interaction module, wherein,

the target detection module is used for collecting information, providing decision-making basis for the driving direction of the intelligent shopping system and collecting human body position information;

the processor module is used for integrating information of the target detection module, the pressure detection module and the ranging module, so that the driving module makes corresponding decisions;

the driving module is used for providing power for the movement of the intelligent shopping system;

the pressure detection module is used for measuring the loading weight of the intelligent shopping system;

the distance measurement module is used for providing an obstacle avoidance function for the intelligent shopping system;

the human-computer interaction module is used for providing an entrance for controlling the whole system for a user, realizing the functions of artificial mode setting and speed selection and displaying a data value for the user;

the power module is used for providing a source of system operation energy.

Further, in the above-mentioned case,

the target detection module comprises a camera;

the camera is internally provided with an STM32H743VIT6 core processor, an OV7725 series sensor is selected, a C language integrated machine vision core algorithm is used in the camera, and a Python programming interface is reserved for a user;

the core algorithm comprises a color block searching algorithm, a research tracking algorithm, an edge detection algorithm, a mark tracking algorithm and a face detection algorithm.

Further, in the above-mentioned case,

the processor module selects an MK60DN512ZVLQ10 processor of Enzhipu company, has 144 pins in total and is provided with a plurality of interfaces of serial ports, a can bus and an IIC bus.

Further, in the above-mentioned case,

the driving module comprises a motor, an incremental photoelectric encoder, a distance measuring sensor and a pressure detection module,

the motor is an RN380 motor, and parameters are shown in the following table

RN380 motor parameter table

The incremental photoelectric encoder mainly comprises four parts, namely a light source generating device, a coded disc, a photosensitive element and an amplifying circuit, wherein the coded disc is provided with a crack with equal width, when the coded disc is driven by a rotating shaft to rotate, the photosensitive element detects that the light source is lost once when the coded disc rotates through one crack, an electric pulse signal is generated through the amplifying circuit, the output signal is three groups of square wave pulses A, B and Z, the rotating direction and the rotating speed are judged according to the phase difference of 90 degrees of A, B two groups of pulses, the Z phase pulse is a zero pulse, and one pulse is output for each rotation;

the distance measuring sensor is a laser distance measuring sensor;

the pressure sensor comprises a 24-bit A/D converter chip and integrates peripheral circuits required by a chip comprising a regulated power supply and an on-chip clock oscillator.

Further, in the above-mentioned case,

the human-computer interaction module is a TFT display screen and is used as an input interface of a user through keys.

Further, in the above-mentioned case,

the power module adopts a 7.2V rechargeable lithium battery.

The invention has the advantages that the invention starts from the perspective of users and shoppers, and mainly solves the problem of heavy burden caused by the distance from home to shopping supermarkets and shopping malls of the users, the traditional automatic following shopping system comprises the modes of infrared guiding following, sonar guiding following, indoor positioning, camera recognition environment and the like, but the shopping system does not recognize the environment, only recognizes the face position information of the human body through the camera, and then moves along with the track of the human body, so that the whole system is simpler, more independent and more flexible.

Drawings

FIG. 1 is a system architecture diagram of the present invention.

Fig. 2 is a schematic diagram of the operation of the encoder of the present invention.

Fig. 3 is a PWM schematic.

FIG. 4 is a circuit diagram of an RTC crystal oscillator.

FIG. 5 is a circuit diagram of a 50M active crystal oscillator.

Fig. 6 is a circuit diagram of the MCU power supply.

FIG. 7 is a circuit diagram of a JTAG interface.

Fig. 8 is a circuit diagram of a reset button.

Fig. 9 shows an interface circuit between OV7725 and STM32H743VIT 6.

Fig. 10 is an OpenMV power supply circuit diagram.

Fig. 11 is an internal circuit diagram of the pressure sensor.

Fig. 12 is an electrical wiring diagram of the laser sensor.

Fig. 13 is an encoder acquisition interface circuit.

Fig. 14 is an isolation circuit.

Fig. 15 is a motor drive circuit diagram.

Fig. 16 is a drive power management block diagram.

Fig. 17 is a step-down circuit diagram.

Fig. 18 is a boosting circuit diagram.

FIG. 19 is a circuit diagram of an interface circuit of a TFT display panel.

Fig. 20 is a key circuit diagram.

FIG. 21 is a diagram of a 3.3V voltage regulator circuit.

FIG. 22 is a diagram of a 5V regulator circuit.

FIG. 23 is a diagram of an adjustable voltage regulator circuit.

Fig. 24 is a diagram of a two-wheel differential motion control model.

Fig. 25 is a face two-dimensional information acquisition diagram.

Fig. 26 is a PID control block diagram.

FIG. 27 is a first algorithm feature template map.

FIG. 28 is a diagram of an overall software system scheme.

FIG. 29 is a block diagram showing the structure of a main routine.

Fig. 30 is a flowchart of an obstacle avoidance routine.

Fig. 31 is a flowchart of the camera subroutine.

Fig. 32 is a timing diagram for pressure sensor data transmission.

Detailed Description

As shown in FIG. 1, the invention provides an automatic following shopping system which liberates both hands of a user, improves the shopping experience of the user as a background and can change the speed along with the change of the weight of a carried object, comprising a processor module, a power supply module, a driving module, a target detection module, a pressure detection module, a distance measurement module and a human-computer interaction module, wherein,

the target detection module is used for collecting information, providing decision-making basis for the driving direction of the intelligent shopping system and collecting human body position information;

the processor module is used for integrating information of the target detection module, the pressure detection module and the ranging module, so that the driving module makes corresponding decisions;

the driving module is used for providing power for the movement of the intelligent shopping system;

the pressure detection module is used for measuring the loading weight of the intelligent shopping system;

the distance measurement module is used for providing an obstacle avoidance function for the intelligent shopping system;

the human-computer interaction module is used for providing an entrance for controlling the whole system for a user, realizing the functions of artificial mode setting and speed selection and displaying a data value for the user;

the power module is used for providing a source of system operation energy.

Further, in the above-mentioned case,

the target detection module comprises a camera;

the camera is internally provided with an STM32H743VIT6 core processor, an OV7725 series sensor is selected, a C language integrated machine vision core algorithm is used in the camera, and a Python programming interface is reserved for a user;

the core algorithm comprises a color block searching algorithm, a research tracking algorithm, an edge detection algorithm, a mark tracking algorithm and a face detection algorithm.

Further, in the above-mentioned case,

the processor module selects an MK60DN512ZVLQ10 processor of Enzhipu company, has 144 pins in total and is provided with a plurality of interfaces of serial ports, a can bus and an IIC bus.

Further, in the above-mentioned case,

the driving module comprises a motor, an incremental photoelectric encoder, a distance measuring sensor and a pressure detection module,

the motor is an RN380 motor, and parameters are shown in the following table

RN380 motor parameter table

Because the invention adopts a wheel type structure, the motion control is the speed control of the motor. The types of motors can be divided into alternating current motors and direct current motors according to different power supply forms. The ac motor needs an ac power supply and its speed regulation needs to be realized by means of a frequency conversion device, so that the ac motor may increase the complexity of the whole system. The invention adopts the direct current motor, and can adjust the rotation speed of the motor only by changing the power supply voltage.

For the selection of the dc power, a corresponding calculation is required by:

F＝μ×M×g

P＝F×V/η

where F is the total friction (N) between the automated shopping system and the ground and μ is the coefficient of friction between the wheels and the ground, typically between 0.01 and 0.3. M is total mass (Kg) of the shopping system, g is universal gravitation constant 9.8, V is operation speed (M/s) of the shopping system, eta is mechanical transmission efficiency, generally about 0.8, and P is motor power (W).

In the present invention, when the shopping system is known to weigh 4Kg and the loading weight is 5Kg, the total weight M is 4+5 and 9 Kg. When the shopping system is about the walking speed of the human body, V is 1 m/s. Mu.0.15. Obtaining:

P＝F×V/η＝μ×M×g×V/η＝0.15×9×9.8×1/0.8＝16.5W

according to the calculation result and fully considering the loading capacity of the shopping system, the RN380 motor is selected, and the main parameters of the RN380 motor are shown in the table 2.1. It can be seen that the RN380 has a rated power of 26.68w, which can meet the requirement of the present invention.

As shown in fig. 2, the incremental photoelectric encoder mainly includes four parts, namely a light source generating device, a code wheel, a photosensitive element and an amplifying circuit, wherein the code wheel is provided with slits with equal width, when the code wheel is driven by a rotating shaft to rotate, the photosensitive element detects that the light source is lost once when the code wheel rotates through one slit, an electric pulse signal is generated through the amplifying circuit, the output signals are three groups of square wave pulses A, B and Z, the rotating direction and the rotating speed are judged according to the phase difference of 90 degrees of A, B two groups of pulses, the Z-phase pulse is a zero pulse, and one pulse is output for each rotation;

the distance measuring sensor is a laser distance measuring sensor;

the pressure sensor comprises a 24-bit A/D converter chip and integrates peripheral circuits required by a chip comprising a regulated power supply and an on-chip clock oscillator.

Further, in the above-mentioned case,

the human-computer interaction module is a TFT display screen and is used as an input interface of a user through keys.

Further, in the above-mentioned case,

the power module adopts a 7.2V rechargeable lithium battery.

The hardware circuit of the present invention is explained below

The minimum system is a minimum hardware circuit unit capable of enabling the MUC to work normally, and the minimum system of the MK60DN512ZVLQ10 mainly comprises a core chip, a crystal oscillator circuit, a power supply circuit, a Jlink interface circuit and a reset key circuit.

MK60DN512ZVLQ10 takes Cortex-M4 as a kernel, and mainly comprises the following available resources inside:

1) FLASH of 512KB, SRAM of 128KB

2)4 PIT timers

3)16 DMA channels

4)3 FTM Module (multifunctional counter, implementation PWM/input capture/quadrature decoding)

5) 2I 2C modules

6)2 LPTMR modules

7)6 UART modules

8)3 SPI modules

The crystal oscillator circuit is used for providing an accurate working clock for a chip, and the crystal oscillator is divided into a passive crystal oscillator and an active crystal oscillator. The crystal oscillator requiring external power supply is called active crystal oscillator. MK60DN512ZVLQ10 internally integrates a Multipurpose Clock Generator Module (MCG) module. The frequency multiplier is used for multiplying the frequency of the crystal oscillator input clock to the system required clock.

MK60DN512ZVLQ10 needs two crystal oscillators, one is the main crystal oscillator of the chip, is used for generating the working clocks of the chip and the peripheral equipment, is equivalent to the pulse of the whole system, and uses the active crystal oscillator of 50 MHZ. The other is a real time timer crystal (RTC) for a clock that counts the accumulated date and time, and a passive crystal of 32.768KHZ is used. Two crystal oscillator circuit diagrams are shown in fig. 4 and 5.

The MK60DN512ZVLQ10 supplies power with 3.3V voltage, and a voltage stabilizing circuit for converting 5V into 3.3V is designed for the convenience of subsequent software program downloading and debugging and for protecting a core chip. As shown in fig. 6.

This circuit is implemented by the integrated chip AMS 1117-3.3. The working principle of the voltage regulator is that the output voltage is sampled and then fed back to the regulating circuit to regulate the impedance of the output stage regulating tube. When the output voltage is low, the impedance of the regulating output stage is reduced so as to reduce the voltage drop of the regulating tube, and when the output voltage is higher, the impedance of the regulating output stage is increased so as to increase the voltage drop of the regulating tube, so that the stability of the output voltage is maintained.

In the figure, C26 and C25 are output filter capacitors, and have the function of suppressing self-oscillation. The output is an oscillating waveform without connecting the two capacitors. C24 and C8 are input capacitors that function to prevent voltage inversion after power down.

The MK60DN512ZVLQ10 chip uses ARM Cortex-M4 kernel, JTAG (Joint Test Action group) interfaces are integrated in the kernel, and the downloading and debugging functions of programs can be realized through the JTAG interfaces. FIG. 7 is a JTAG interface circuit.

The reset is divided into an external reset and an internal reset. The external reset comprises power-on reset and reset by pressing a reset button. Internal reset has a watchdog timer reset, a low voltage reset, a low drain wakeup (LLWU) reset, an MCG lost clock reset, a software reset, a lock reset, an EzPort reset, etc. The key reset belongs to the reset by pressing a reset button in external reset, and the function of the key reset is to ensure that the MCU starts to work all over again. Mainly in the software program

The MCU debugging device is used during downloading and debugging, and aims to prevent the situation that the MCU cannot work normally due to the occurrence of program problems. The circuit diagram is shown in figure 8.

The sensor signal acquisition circuit of the present invention is described below

The core idea of the invention is to collect different external information through a sensor, and then perform corresponding processing through the MCU, thereby controlling the automatic shopping system to move along. The main sensors for signal acquisition are OpenMV cameras (target detection module), pressure sensors (pressure detection module) and laser sensors (distance measurement module). The internal hardware structure of the sensor and the interface circuit with the processor will be described separately below.

OpenMV is a camera with a core processor, the internal circuit of the camera is complex, and the camera is provided with a minimum system circuit of a processor STM32H743VIT6, a camera acquisition circuit, a USB interface circuit, an SD card storage circuit and the like. The present invention only describes the circuit applied to the OpenMV functional resources, which includes the interface circuit of the OV7725 camera and STM32H743VIT6, the interface circuit of STM32H743VIT6 and MK60DN512ZVLQ10, and the power circuit.

The OV7725 is a color camera with 30W pixels, and is widely applied to the field of image acquisition. The control mode of the method is to configure the register through an SCCB interface protocol, and the SCCB interface is I2C essentially. The I2C interface can realize control of each device by unique address identification access of the cluster, thereby performing white balance, gama, color correction, exposure control and the like. OV7725 image data is transmitted over an 8-bit interface, which can achieve a frame rate of 60fps in VGA mode. The interface circuit of OV7725 and STM32H743VIT6 is shown in FIG. 9.

Referring to FIG. 1, the target detection module is interfaced with the core processor

And carrying out data transmission through a UART serial port, wherein the STM32H743VIT6 and MK60DN512ZVLQ10 interface circuit is a serial port communication circuit. The interface circuit diagram is shown in 3.9. Wherein, TXD and RXD are serial data pins of the chip, and the TX and RX of the chip and the chip need to be reversely connected.

OpenMV has two kinds of power supply interfaces, one is a USB power supply interface, and the other is a pin header power supply interface. OpenMV supplies power for 5V, and a 3.3V voltage output interface is reserved. The circuit diagram is shown in fig. 10.

The pressure sensor acquisition circuit of the present invention is described below

According to the embedded system block diagram of the auto follow shopping system of FIG. 1, the pressure sensor interfaces with the core processor for data transmission via the I/O port. The protocol used by the interface is similar to the protocol I2C, and consists of a clock line and a data line, but the clock line is not generated by a clock signal, and the high and low levels are continuously changed by controlling the I/O port of the MCU, so that the clock effect is achieved, and the time sequence is different from that of the protocol I2C. The pressure sensor core is an HX711 integrated chip, and the internal circuit diagram of the pressure sensor core is shown in FIG. 11.

As shown in fig. 11, the present invention provides a pressure sensing circuit, which includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, an HX711 chip, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first triode;

the first end of the first capacitor is grounded, and the second end of the first capacitor is respectively connected with the E pole of the first triode and the VSUP port of the HX711 chip;

the first end of the second capacitor is connected with an AVDD port of the HX711 chip, and the second end of the second capacitor is connected with the first end of the third capacitor;

the first end of the third capacitor is connected with an AGND port of the HX711 chip, and the second end of the third capacitor is connected with a VBG port of the HX711 chip;

the first end of the fourth capacitor is connected with an INNA port of the HX711 chip, and the second end of the fourth capacitor is connected with an INPA port of the HX711 chip;

the first end of the first resistor is respectively connected with the C pole of the first triode and the AVDD port of the HX711 chip, and the second end of the first resistor is respectively connected with the first end of the second resistor and the VFB port of the HX711 chip;

the first end of the second resistor is connected with the VFB port of the HX711 chip, and the second end of the second resistor is connected with the first end of the third capacitor;

the first end of the third resistor is connected with the first port of the sensor, and the second end of the third resistor is connected with the second end of the fourth capacitor;

the first end of the fourth resistor is connected with the second port of the sensor, and the second end of the third resistor is connected with the first end of the fourth capacitor;

a third port of the sensor is connected with a first end of a second capacitor;

the fourth port of the sensor is grounded;

the B pole of the first triode is connected with the BASE port of the HX711 chip.

Further, in the above-mentioned case,

the VSUP port of the HX711 chip is connected with a power supply of a voltage stabilizing circuit, and the range of the power supply of the voltage stabilizing circuit is 2.6-5.5V;

the AVDD port of the HX711 chip is connected with an analog power supply, and the range of the analog power supply is 2.6-5.5V;

the HX711 chip AGND is grounded;

and the HX711 chip VBG is connected with a reference power supply output port.

HX711 is a 24-bit A/D converter chip designed specifically for high precision electronic scales. Compared with other chips of the same type, the HX711 integrates peripheral circuits required by other chips of the same type, such as a voltage-stabilized power supply, an on-chip clock oscillator and the like, and has the advantages of high integration level, high response speed, high anti-interference performance and the like. The cost of the whole electronic scale is reduced, and the performance and the reliability of the whole electronic scale are improved. The interface and programming of the chip and the rear end MCU chip are very simple, all control signals are driven by pins, and the programming of a register in the chip is not needed. The input selection switch can arbitrarily select the channel A or the channel B and is connected with the low-noise programmable amplifier inside the input selection switch. The programmable gain for channel a is 128 or 64, and the corresponding full scale differential input signal amplitude is 20mV or 40mV, respectively. Channel B is then a fixed 32 gain for system parameter detection. The stabilized voltage power supply provided in the chip can directly provide power for the external sensor and the A/D converter in the chip, and no additional analog power supply is needed on a system board. The on-chip clock oscillator does not require any external devices. The power-on automatic reset function simplifies the initialization process of starting.

The pressure sensor and the interface of the core processor carry out data transmission through the I/O port, and the interface diagram is shown in FIG. 2. The protocol used by the interface is similar to the protocol I2C, and consists of a clock line and a data line, but the clock line is not generated by a clock signal, and the high and low levels are continuously changed by controlling the I/O port of the MCU, so that the clock effect is achieved, and the time sequence is different from the protocol I2C.

HX711 is a serial data bus type A/D converter. As a serial communication mode, it is important to grasp the timing diagram of the device for use and operation. The serial communication line consists of pins PD-SCK and DOUT and is used for outputting data, selecting an input channel and gain. When the data output pin DOUT is at a high level, indicating that the a/D converter is not ready to output data, the serial clock input signal PD-SCK should be at a low level. PD-SCK should input 25 to 27 unequal clock pulses when DOUT goes low from high. Wherein the rising edge of the first clock pulse will read out the Most Significant Bit (MSB) of the output 24 bits of data until the 24 th clock pulse is used to select the input channel and gain for the next a/D conversion. The timing sequence is shown in FIG. 3:

HX711 can generate VAVDD and AGND voltages, i.e., the E + and E-voltages on the 711 module. This voltage is calculated by VAVDD ═ VBG (R1+ R2)/R2. VBG is the module reference voltage 1.25v, R1 ═ 20K, and R2 ═ 8.2K.

Thus, VAVDD is 4.3V

The maximum output voltage of the sensor of 5Kg under the supply voltage of 4.3V is 4.3V 1 mV/V-4.3 mV

After 128 times of amplification, the maximum voltage is 4.3mV 128-550.4 mV

The maximum 24-bit digital value output after AD conversion is as follows: 550.4mV 2^24/4.3V ≈ 21474 assuming that the weight is A Kg, (x <5Kg), the measured AD value is y

5Kg sensor output, voltage sent to AD module is A Kg 4.3mV/5Kg 0.86A mV, after 128 times gain, 128X 0.86A 110.08AmV

Converting to 24bit digital signal of 110.08A mV 2^24/4.3V ^ 429496.7296A

So that y is 429496.7296A/100 is 4294.967296A

Thus, it is found that (y/4294.967296) Kg ≈ y/4.30g

Because the slope characteristics of the different sensors are different, each sensor needs to correct the 4.30 divisor. When the measured weight is found to be excessive, the value is increased. If the measured weight is smaller, the change value is decreased. This value is generally between 4.0 and 5.0. Depending on the linear slope of the sensor. Each sensor is calibrated. If the measured value of the sensor is larger, the value needs to be increased, and if the measured value of the sensor is smaller, the value needs to be decreased.

The pressure sensor circuit provided by the invention has the advantages of good stability and high reliability, and can meet the requirements of a high-precision pressure sensor on the sensor circuit.

The laser sensor acquisition circuit is explained below.

The laser sensor is used as a main device for detecting obstacles, and the laser sensor selected by the invention is a sky L1 type laser ranging sensor of Myantenna company. The electrical wiring diagram is shown in fig. 12. The sensor has a serial port communication mode and an I2C communication mode, the invention selects a simple and stable serial port communication mode, and has the following characteristics:

the distance of the target object is sensed through detecting the laser phase difference, and the resolution ratio of millimeter level can be achieved;

the temperature adaptability is strong, and the drift amount is small;

the high signal-to-noise ratio ensures that the color, the surface roughness, the material and the like of the target have little influence on the detection structure;

the volume is small, and the use is convenient;

the following describes the encoder acquisition circuit of the present invention

The selected encoder is a 1024-line Mini encoder of a flying-by-flying science and technology company, and has the characteristics of small volume (diameter 15 x length 18mm), light weight (11.22 g), high precision, strong anti-interference capability (capable of working in a multi-dust and humid environment) and the like. The wiring diagram to the MCU processor is shown in fig. 13. The core processor collects the pulse signal returned by the encoder through the orthogonal decoding function of the FTM module, so that the running speed of the automatic following shopping system is obtained.

The drive control circuit of the present invention will be explained below.

The drive control circuit of the system is mainly used for amplifying signals in the MCU circuit, so that the control of the motor is realized. The automatic following shopping system adopts a two-wheel and two-drive mode, so that the drive control circuit is driven by two ways. And according to the function requirement, the shopping system needs a reversing function, so that each way is controlled by two paths of PWM. The positive and negative rotation of the motor is realized by controlling the duty ratio of the two paths of PWM. The driving circuit of the invention comprises three parts, namely a signal isolation circuit (and an interface circuit of the MCU), a motor driving circuit and a power circuit.

The motor-driven isolation circuit is mainly used for preventing the phenomenon that when the motor is powered off, the MUC is broken down by the large induction voltage generated by the coil winding inside the motor. The circuit diagram is shown in fig. 14.

Because the driving capability of the output signal of the singlechip is limited, a motor driving circuit is introduced. The whole working process is that the single chip microcomputer is used for making common driving signals to drive a high-power tube such as a Mos tube so as to generate large current to drive the motor, and the signal space ratio can control the average voltage applied to the motor through a driving chip so as to realize the adjustment of the rotating speed.

The motor driving circuit adopted by the invention is a circuit constructed by the IR2104 chip and the H bridge, and the circuit diagram is shown in FIG. 15. The H-bridge is a typical dc motor control circuit, the motor is located in the middle of the H-bridge, and in order to operate the motor, a pair of switches on the diagonal line must be turned on, and the forward and reverse rotation of the motor is controlled through different current directions.

The main chips in the whole driving module are HCPL2630(5V power supply) and IR2104(12V power supply), but the power supply voltage is 7.2V. Its power supply circuit needs both a buck and a boost. A block diagram of power management in the driver module is shown in fig. 16.

The voltage reduction circuit adopts an LM7805 chip and has the characteristics of small output voltage ripple, convenience in use and the like. The voltage step-down circuit diagram is shown in fig. 17. The C3 capacitor is required by LM7805 voltage stabilization integrated circuit, and is used for stabilizing the working state of LM7805 internal amplifier and improving the transient response of voltage regulation. The capacitance value of C3 is specified by manufacturers and must not be less than 0.1 uF. C1 and C2 are load circuit decoupling capacitors whose values are related to the load operation mode.

The boost circuit adopts an MC34063 chip which is commonly used in power supply processing and can realize the functions of boosting, reducing voltage, reversing the polarity of a power supply and the like, and the boost circuit is shown in figure 18.

The formula of the output voltage is as follows:

V_out＝1.25×(1+R₃/R₁)

according to the output voltage formula, the output voltage is only equal to R₃、R₁The values are relative, and are constant because 1.25V is the reference voltage. The output voltage is constant value 12V, then R₃And R₁The ratio should be around 8.6.

The man-machine interaction module of the present invention is explained below.

The man-machine interaction module selected by the invention is composed of a TFT display screen and a key. The interface circuit between the TFT display and the MCU is shown in FIG. 19. The communication mode is SPI serial port communication and 3.3V voltage power supply. Its internal chip is ST7735, can carry on the color image display.

The key circuit is shown in fig. 20, and provides a selection and input interface for a user. The total number of 5 keys is designed, the keys 1 and 2 are mainly used for selecting up and down cursors, the keys 3 and 4 are mainly used for adjusting numerical values, the Key3 is minus, the Key4 is plus, and the Key5 is a definite Key.

The power supply circuit of the present invention is explained below.

According to a 2.10-section power supply design block diagram, the system supplies and requires 3 different voltages, namely 3.3V, 5V and 7.2V. The power supply is supplied with 7.2V, so the power supply voltage needs to be reduced to 3.3V and 5V. For flexibility of the system, the system selects voltage stabilizing modules sharing 3 paths of voltage stabilizing circuits, namely 3.3V voltage stabilizing, 5V voltage stabilizing and adjustable voltage stabilizing. The adjustable voltage stabilizing circuit mainly performs the function of 5V power supply.

As shown in FIG. 21, the 3.3V voltage regulator circuit adopts an SPX29300 chip and has 3 pins. The SPX2930 series of chips has two typical application circuits, a fixed output circuit and an adjustable output circuit. The output voltage has the characteristics of stability, small ripple, large current and the like.

As shown in fig. 22, the 5V regulator circuit is a monolithic buck-type switch mode converter using an MP2482 chip and has a built-in 50m Ω internal power MOSFET switch.

The input voltage is 4.5V to 30V, and the calculation formula of the output voltage is as follows:

the output voltage of the circuit is 5V, and R can be obtained₁₁And R₁₂The ratio of (A) to (B) is about 5.25, so that the resistance R is obtained₁₂Is 5.1K, and a resistance R₁₁Has a resistance of 27K.

As shown in FIG. 23, the chip used for the adjustable voltage regulator circuit is AS1015,. The left side is input voltage, the right side is output, R1 is a slide rheostat, and the output voltage of the slide rheostat can be adjusted through a resistor R1. The output voltage formula is:

because the adjustable voltage stabilizing circuit of the invention needs to output 5V voltage, according to the formula, R₃And R₁The ratio of (A) to (B) is about 5.25. According toCircuit R₃To fix the resistance value of 1K, R is required to be adjusted₁The resistance value is modulated to be about 0.19K.

The following explains the automatic following algorithm of the present invention.

The automatic following shopping system is of a three-wheel structure, two wheels are driving wheels, and one wheel is a supporting wheel, so that the overall motion control of the shopping system is realized by two wheels. As shown in fig. 24, a kinematic model of two-wheel differential control was constructed.

The kinematic model defines the linear velocities of the left and right drive wheels at Vl and Vr, respectively, with initial moments Vl1 and Vr 1. Wherein the midpoint of the two drive wheels is A1 and A1 is represented by (x1, y1) in coordinate system XOY. The instantaneous speed of the shopping system is V1, the instantaneous angular speed is omega 1, beta 1 is the included angle between the linear speed and the X axis, L is the distance between two driving wheels, theta 1 represents the rotation angle of the initial position and the next moment position, wherein theta 1 is theta 2, and R is the rotation radius of the shopping system. The shopping system location information can be represented by a vector P ═ x, y, β ] T.

The instantaneous line speed V1 expression for the shopping system is:

the expression for the instantaneous angular velocity ω 1 is:

the radius of the shopping system in the rotation process can be calculated by combining the formula:

the shopping system motion model can be obtained as follows:

the following describes the implementation of the automatic following algorithm of the present invention

The movement position of the shopping system is related to the linear speeds of the left wheel and the right wheel and the distance L between the left wheel and the right wheel, and in practice, L is a fixed value and is followed by a human body mainly by controlling the rotating speeds of the two wheels. The automatic following algorithm mainly identifies the face position information through the camera, utilizes the deviation of the face position information as input, and then uses the PID algorithm to control the rotating speed of the left wheel and the right wheel of the shopping system, thereby ensuring that the shopping system can stably follow the movement of the human body.

The automatic following shopping system acquires face position information by means of an OpenMV camera, and a two-dimensional coordinate system is constructed according to a two-dimensional image acquired by the camera, as shown in FIG. 25. The point C is the normal viewpoint of the image, and the coordinates (x0, y0) are the center coordinates of the image and also the reference coordinates of the face position. If (x1, y1) is the actual coordinates of the face, the information of the deviation of the face position is (x1-x0, y1-y 0).

The PID algorithm, one of the most classical control algorithms, represents proportional (P), integral (I), and derivative (D) control, respectively. The proportion link mainly reflects a deviation signal (the system mainly reflects the position deviation of the human face) in the control system, and if the deviation signal is generated, the controller acts to further reduce the deviation; the integration link mainly eliminates steady-state errors and improves the zero-difference degree of the system; the differential link reflects the variation trend of the deviation signal and can accelerate the adjustment speed of the control system.

A PID control block diagram of the auto-follow shopping system is shown in fig. 26. The system has two feedback structures, wherein the main feedback takes the center coordinates (x0, y0) of an image collected by a camera as an input signal, a deviation signal is generated through the position coordinates (x1, y1) of the face actually fed back by the camera, then a corresponding motor driving signal is generated through proportional regulation, integral regulation and differential regulation of PID, and finally the position and the posture of a shopping system are changed so as to change the actual face position information collected by the OpenMV camera. The local feedback has the function of carrying out speed measurement feedback on the motor through the encoder, so that the aim of accurately controlling the rotating speed of the motor is fulfilled.

The conventional PID calculation formula is as follows:

where Kp, Ki, Kd are constant coefficients, and e (k) is the deviation between the input signal and the feedback signal.

According to FIG. 26, the automatic follow-up shopping system has two feedback links, and combines with the traditional PID calculation formula, the following formula is listed:

u(k)＝u₁(k)+u₂(k)+u₃(k)

the face recognition algorithm of the present invention is explained below.

Face detection is classified into the computer vision category, which is mainly divided into face discrimination and face recognition. Different faces need to be distinguished in face distinguishing, a large amount of sample data is needed, and whether the detected faces are the needed targets or not is judged by comparing the collected faces with the sample data. The face recognition only needs to detect whether the face exists or not, and does not need to judge different faces. According to basic function requirements of the automatic following shopping system and complexity consideration of the overall design, a face recognition mode is selected, and a following target is the largest face in an image.

The OpenMV realizes the face recognition by adopting a first algorithm, so that the face can be quickly found in the image, and the position information of the face is returned. The first algorithm is a feature extraction algorithm for grayscale images, and mainly distinguishes human faces from non-human faces by a feature template as shown in fig. 27. As can be seen from fig. 27, there are two rectangles of different colors, black and white, in the feature template, and the feature value of the template is defined as the sum of the pixel values corresponding to the white rectangles minus the sum of the pixels corresponding to the black rectangles, and the feature value reflects the change of the gray image. For the A, C templates in the figure, the calculation formula of the characteristic value is as follows:

s ∑ white rectangular pixel- Σ black rectangular pixel

For the B template, the characteristic value calculation formula is as follows:

s ═ sigma white rectangular pixels-2 ∑ black rectangular pixels

In the first algorithm, by changing the size and position of the feature template, it is desirable that the difference between the feature value calculated by placing the rectangular feature template in the face region and the feature value calculated by placing the rectangular feature template in the non-face region is larger, so that how to select a proper feature template and improve the speed of feature value calculation becomes a difficulty in the use of the first algorithm. The selection of the characteristic template can be trained through an AdaBoost algorithm, and the calculation speed of the characteristic value can be improved through an integral graph method. Adaboost is an iterative algorithm, and the core idea thereof is to train different classifiers (weak classifiers) aiming at the same training set, and then to assemble the weak classifiers to form a stronger final classifier (strong classifier).

The software system of the present invention is explained below

According to the overall design concept, the system collects external information through the sensor, then controls the shopping system to move along with the human body, and designs the overall scheme of the software system shown in fig. 28, wherein the software design mainly comprises information collection, information processing and information execution.

The main program design takes the MCU as the main control idea, the block diagram is shown in FIG. 29, the system performs initialization operation after power-on reset or key reset, firstly, the MCU is initialized internally, such as initialization of I/O, a timer, interruption and the like; secondly, carrying out corresponding initialization operation on external equipment, such as laser ranging, a pressure sensor, a display screen and the like; then opening an interrupt and a timer, and entering the program into a main cycle; and then, judging a Flag variable Flag, wherein the initial value is 0, the value is correspondingly set according to the keys, the total value is divided into 3 different modes, and the functions are as follows:

1) flag ═ 0: and in the waiting mode, waiting for the user to perform key operation and selecting the corresponding functional mode.

2) Flag ═ 1: if the front part is judged to be free from obstacles, the OpenMV face recognition is carried out to acquire the position information of the human body, and then the internal parameters are automatically adjusted by a program according to the size of the value acquired by the pressure sensor; if the obstacle exists in the front, Flag is set to 0, and the operation returns to the waiting stage.

3) Flag ═ 2: when the program enters the parameter adjusting mode, the internal parameters can be adjusted through the keys, the Flag is set to be 0 when the program exits, and the program returns to the waiting stage.

The obstacle avoidance module is realized by a laser sensor, and a communication protocol between the laser sensor and the core processor adopts UART (universal asynchronous receiver/transmitter), so that an obstacle avoidance subprogram mainly completes serial port driving of the laser sensor. After power-on, the UART port of the MCU is initialized first, and then the configuration of the laser ranging function is performed, the format of the ascil text communication protocol for the laser sensor is as shown in table 5.1.

Table ascil text communication protocol format

The invention selects the continuous measurement function, the MCU sends the character 'iACM' to the laser sensor through the serial port, and the function sent by the serial port is as follows: UART _ putfuff (UART3, "iACM", 2); wherein the parameter UART3 of the function indicates that serial port 3 is selected for transmission, and 2 indicates that 2 characters are transmitted in total.

The shopping system needs to continuously detect whether an obstacle exists in front or not (the detection distance is less than 0.20m), and if so, the system brakes emergently to wait for the user to perform the next operation. Fig. 30 is a flowchart of an obstacle avoidance routine.

Following OpenMV face recognition subprogram design

The OpenMV camera has the main function of recognizing face information and returning face position information to the core processor through a UART protocol, so that related functions of camera initialization, face recognition, serial port communication and the like are mainly completed by OpenMV camera subprograms. Since OpenMV is a camera with a processor and a Python programming interface is reserved for a user, program operation thought is mainly considered when program design is carried out, and excessive design is not required for a hardware bottom driver. A subroutine flowchart thereof is shown in fig. 31.

The main program codes of the OpenMV camera are as follows:

img＝sensor.snapshot()

objects＝img.find_features(face_cascade,threshold＝0.75, scale_factor＝1.25)

face＝find_max(objects)

the following describes the sub-programming of the pressure sensor

The pressure sensor is mainly used for detecting the weight of goods loaded in the shopping system, the subprogram of the pressure sensor is mainly designed to be initialized, and then the core processor continuously receives pressure data of the pressure sensor. The pressure sensor and the processor are connected in two, and the MCU initializes one interface as output and one interface as input. As shown in fig. 32, the MCU first sets the output port to low level, waits for the input port to transmit data, then the output port generates 24 falling edges, reads the input port data at the falling edge, and performs the receive port data conversion when the 25 th falling edge arrives, where the data conversion code is count ^0x800000 and the variable count is pressure data.

Following sub-programming of the motor drive

The rotation principle of the motor is that voltage is added to two ends of the motor, the rotation speed of the motor is determined by the voltage value, and the higher the voltage is, the higher the rotation speed of the motor is. The invention adopts a direct current motor, can adjust the rotation speed of the motor only by changing the power supply voltage, and adopts a Pulse Width Modulation (PWM) method to change the voltage value.

In PWM drive control, the power supply is first turned on and off at a fixed frequency, and the length of the "on" and "off" times in a cycle is varied as needed. The motor speed is controlled by changing the magnitude of the flat average voltage by changing the "duty cycle" of the voltage on the armature of the dc motor, which is schematically shown in fig. 3.

As shown, the formula is available:

V_d＝V_max×D

D＝t₁/T＝(T-t₂)/T

vd motor average speed, Vmax and Vmin are motor maximum speed and minimum speed, and D is duty ratio. When I change the duty ratio, the purpose of speed regulation can be achieved.

According to the invention, a switch is not required to be independently arranged to realize PWM, and the average value of the voltage is changed by controlling the high-low level time of the processor pin, wherein the high level corresponds to 'on' and the low level corresponds to 'off'. Each motor adopts two paths of PWM interfaces, so that the forward and reverse rotation of the motor is controlled. The frequency setting of the motor is obtained by frequency division of a processor bus clock, and the initialization part codes of the motor control interface of the core controller are as follows:

FTM _ pwm _ init (FTM0, FTM _ CH5,15 x 1000, 0); // PWM initialization

ftm_pwm_init(FTM0,FTM_CH6,15*1000,0)；

ftm_pwm_init(FTM0,FTM_CH3,15*1000,0)；

ftm_pwm_init(FTM0,FTM_CH4,15*1000,0)；

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. An intelligent shopping system is characterized by comprising a processor module, a power supply module, a driving module, a target detection module, a pressure detection module, a distance measurement module and a man-machine interaction module, wherein,

the target detection module is used for collecting information, providing decision-making basis for the driving direction of the intelligent shopping system and collecting human body position information;

the processor module is used for integrating information of the target detection module, the pressure detection module and the ranging module, so that the driving module makes corresponding decisions;

the driving module is used for providing power for the movement of the intelligent shopping system;

the pressure detection module is used for measuring the loading weight of the intelligent shopping system;

the distance measurement module is used for providing an obstacle avoidance function for the intelligent shopping system;

the human-computer interaction module is used for providing an entrance for controlling the whole system for a user, realizing the functions of artificial mode setting and speed selection and displaying a data value for the user;

the power module is used for providing a source of system operation energy.

2. The intelligent shopping system as claimed in claim 1,

the target detection module comprises a camera;

the camera is internally provided with an STM32H743VIT6 core processor, an OV7725 series sensor is selected, a C language integrated machine vision core algorithm is used in the camera, and a Python programming interface is reserved for a user;

the core algorithm comprises a color block searching algorithm, a research tracking algorithm, an edge detection algorithm, a mark tracking algorithm and a human face detection algorithm.

3. The intelligent shopping system as claimed in claim 1,

the processor module selects an MK60DN512ZVLQ10 processor of Emuzpu company, has 144 pins in total and has a plurality of interfaces of a serial port, a can bus and an IIC bus.

4. The intelligent shopping system as claimed in claim 1,

the driving module comprises a motor, an incremental photoelectric encoder, a distance measuring sensor and a pressure detection module,

the motor is an RN380 motor, and parameters are shown in the following table

RN380 motor parameter table

The incremental photoelectric encoder mainly comprises four parts, namely a light source generating device, a coded disc, a photosensitive element and an amplifying circuit, wherein the coded disc is provided with a crack with equal width, when the coded disc is driven by a rotating shaft to rotate, the photosensitive element detects that the light source is lost once when the coded disc rotates through one crack, an electric pulse signal is generated through the amplifying circuit, the output signal is three groups of square wave pulses A, B and Z, the rotating direction and the rotating speed are judged according to the phase difference of 90 degrees of A, B two groups of pulses, the Z phase pulse is a zero pulse, and one pulse is output for each revolution;

the distance measuring sensor is a laser distance measuring sensor;

the pressure sensor comprises a 24-bit A/D converter chip and integrates peripheral circuits required by a chip comprising a regulated power supply and an on-chip clock oscillator.

5. The intelligent shopping system as claimed in claim 1,

the human-computer interaction module is a TFT display screen and is used as an input interface of a user through keys.

6. The intelligent shopping system as claimed in claim 1,

the power module adopts a 7.2V rechargeable lithium battery.

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