circuit design

• 2-way ultrasonic distance sensor
  
• MPU6050 attitude sensor
  
• Can be externally connected to ESP32-CAM to transmit real-time video
  
• 2S lithium battery balance charging, using TP5100 solution
  
• With battery voltage monitoring and charging status monitoring
  

structural design

Material costs

1. Screws and other hardware￥34
   
1. Several M3X8, M3X12, M3X16 large flat head screws
   
2. Several M3 nuts
   
3. Several M3 knurled nuts
   
4. M3 lock nut x8
   
5. M4X8 large flat head screw x32
   
6. M4 lock nut x32
   
7. Stainless steel washer 3*6*0.5 x40
   
8. Nylon washer 3*12*1 x8
   
2. Bearing￥37
   
1. Inner diameter 3 Outer diameter 8 Thickness 3 x20
   
2. Inner diameter 9 Outer diameter 14 Thickness 3 x 4
   
3. Acrylic shell￥30
   
4. MG995 steering gear (8 pieces)￥100
   
5. 25T aluminum alloy steering gear arm (4 pieces)￥20
   
6. 25T aluminum alloy steering gear disc (4 pieces)￥10
   
7. Battery (three-wire interface 7.4V2200mAh)￥23
   

software design

STC8G2K64S4

ITCAST-HI3861

Robot dog debugging software

#define LEG_R1 80.0f // Thigh length
#define LEG_R2 82.0f // Calf length
#define LEG_R3 22.0f // Calf fulcrum length
#define LEG_R4 80.0f // Calf link length
#define LEG_R5 24.0832f // Linkage bracket radius
#define LEG_A5 96.73f // Linkage bracket arc angle
#define LEG_R6 30.0f // Thigh link length
#define LEG_R7 20.6f // Servo arm radius
#define SERVO_DIST_V 20.0f // AB servo axis vertical distance
#define SERVO_DIST_H 21.2f // AB servo axis horizontal distance

#define SERVO_DIST_D sqrt((SERVO_DIST_V * SERVO_DIST_V) + (SERVO_DIST_H * SERVO_DIST_H))
#define DEG_TO_RAD(A) ((A) * M_PI / 180.0)
#define RAD_TO_DEG(A) ((A) * 180.0 / M_PI)

void inverse(struct Point_t p, double* output) {
    double d2 = px * px + py * py;
    double d = sqrt(d2);
    double a = (d2 + ((LEG_R1 * LEG_R1) - (LEG_R2 * LEG_R2))) / (2.0 * d);
    double o1 = acos(a / LEG_R1);
    double o2 = acos(py / d);
    double o3 = o1 + acos((d - a) / LEG_R2);
    double k2 = ((LEG_R1 * LEG_R1) + (LEG_R3 * LEG_R3)) - (2.0 * LEG_R1 * LEG_R3) * cos(o3);
    double k = sqrt(k2);
    double m1 = acos((k2 + ((LEG_R1 * LEG_R1) - (LEG_R3 * LEG_R3))) / ((2.0 * LEG_R1) * k));
    double m2 = acos((k2 + ((LEG_R5 * LEG_R5) - (LEG_R4 * LEG_R4))) / ((2.0 * LEG_R5) * k));
    double m3 = px > 0.0 ? o1 - o2 : o1 + o2;
    double m4 = (2.0 * M_PI - DEG_TO_RAD(LEG_A5) - acos(SERVO_DIST_V / SERVO_DIST_D)) - m1 - m2 - m3;
    double g2 = ((LEG_R5 * LEG_R5) + (SERVO_DIST_D * SERVO_DIST_D)) - (2.0 * LEG_R5 * SERVO_DIST_D) * cos(m4);
    double g = sqrt(g2);
    double t1 = acos((g2 + ((SERVO_DIST_D * SERVO_DIST_D) - (LEG_R5 * LEG_R5))) / ((2.0 * SERVO_DIST_D) * g));
    double t2 = acos((g2 + ((LEG_R7 * LEG_R7) - (LEG_R6 * LEG_R6))) / ((2.0 * LEG_R7) * g));
    double t3 = acos(SERVO_DIST_H / SERVO_DIST_D);
    double servo_A = 45.0 - RAD_TO_DEG(m3);
    double servo_B = 135.0 - RAD_TO_DEG(t1 + t2 + t3);
    output[0] = servo_A;
    output[1] = servo_B;
}

Physical display

There is a problem

• After the actual installation, with the battery in hand, the weight exceeds 1KG. Replacing the acrylic shell with a carbon fiber board should reduce a lot of weight and increase strength.
  
• The current continues to be around 2A during operation, and the battery life is poor when using a 2200mAh 7.4V battery (it is later envisaged to add a wireless charging module to the chassis and automatically navigate for charging).
  
• Because the lithium battery charge management chip TP5100 was burned during the debugging process, the lithium battery balance charge and discharge could not be tested.
  

Video display