Arduino Bluetooth Robot

1#include <AFMotor.h>
2
3AF_DCMotor motor1(1, MOTOR12_1KHZ); 
4AF_DCMotor  motor2(2, MOTOR12_1KHZ); 
5AF_DCMotor motor3(3, MOTOR34_1KHZ);
6AF_DCMotor motor4(4,  MOTOR34_1KHZ);
7
8char command; 
9
10void setup() 
11{       
12  Serial.begin(9600);  
13}
14
15void loop(){
16  if(Serial.available() > 0){ 
17    command = Serial.read();  
18    Stop();
19    switch(command){
20    case 'F':  
21      forward();
22      break;
23    case 'B':  
24       back();
25      break;
26    case 'L':  
27      left();
28      break;
29    case 'R':
30      right();
31      break;
32    }
33  } 
34}
35
36void forward()
37{
38  motor1.setSpeed(255); 
39  motor1.run(FORWARD);
40  motor2.setSpeed(255); 
41  motor2.run(FORWARD); 
42  motor3.setSpeed(255);
43  motor3.run(FORWARD); 
44  motor4.setSpeed(255);
45  motor4.run(FORWARD); 
46}
47
48void  back()
49{
50  motor1.setSpeed(255);
51  motor1.run(BACKWARD);
52  motor2.setSpeed(255);
53  motor2.run(BACKWARD);
54  motor3.setSpeed(255); 
55  motor3.run(BACKWARD); 
56  motor4.setSpeed(255); 
57  motor4.run(BACKWARD);
58}
59
60void left()
61{
62  motor1.setSpeed(255); 
63  motor1.run(BACKWARD); 
64  motor2.setSpeed(255);  
65  motor2.run(BACKWARD);
66  motor3.setSpeed(255); 
67  motor3.run(FORWARD);  
68  motor4.setSpeed(255); 
69  motor4.run(FORWARD);  
70}
71
72void right()
73{
74  motor1.setSpeed(255);
75  motor1.run(FORWARD); 
76  motor2.setSpeed(255); 
77  motor2.run(FORWARD); 
78  motor3.setSpeed(255);
79  motor3.run(BACKWARD); 
80  motor4.setSpeed(255); 
81  motor4.run(BACKWARD); 
82} 
83
84void Stop()
85{
86  motor1.setSpeed(0); 
87  motor1.run(RELEASE); 
88  motor2.setSpeed(0);
89  motor2.run(RELEASE);  
90  motor3.setSpeed(0); 
91  motor3.run(RELEASE); 
92  motor4.setSpeed(0); 
93  motor4.run(RELEASE); 
94}