diff --git a/Core/Inc/motor.h b/Core/Inc/motor.h
index d20f3d3..35d7a45 100644
--- a/Core/Inc/motor.h
+++ b/Core/Inc/motor.h
@@ -5,8 +5,6 @@
 
 #include "main.h"
 
-// duty in [-100, 100]
-
 void MOTOR_Start(void);
 void MOTOR_Slip(void);
 void MOTOR_Stop(void);
diff --git a/Core/Src/motor.c b/Core/Src/motor.c
index f1b8041..33d20f5 100644
--- a/Core/Src/motor.c
+++ b/Core/Src/motor.c
@@ -17,6 +17,8 @@ void MOTOR_Start(void)
 	HAL_TIM_PWM_Start(MOTOR_TIM, MOTOR_R_CHAN);
 }
 
+/// @brief 自由滑行
+/// @param  
 void MOTOR_Slip(void)
 {
 	HAL_GPIO_WritePin(L_FORWARD_GPIO_Port, L_FORWARD_Pin | L_BACKWARD_Pin | R_FORWARD_Pin | R_BACKWARD_Pin, GPIO_PIN_RESET);
@@ -24,6 +26,8 @@ void MOTOR_Slip(void)
 	__HAL_TIM_SetCompare(MOTOR_TIM, MOTOR_R_CHAN, MAX_SPEED);
 }
 
+/// @brief 刹车
+/// @param  
 void MOTOR_Stop(void)
 {
 	HAL_GPIO_WritePin(L_FORWARD_GPIO_Port, L_FORWARD_Pin | L_BACKWARD_Pin | R_FORWARD_Pin | R_BACKWARD_Pin, GPIO_PIN_RESET);
@@ -31,6 +35,10 @@ void MOTOR_Stop(void)
 	__HAL_TIM_SetCompare(MOTOR_TIM, MOTOR_R_CHAN, 0);
 }
 
+/// @brief 控制电机占空比
+
+/// @param leftDuty 绝对值 20-100, 支持正负
+/// @param rightDuty 绝对值 20-100，支持正负
 void MOTOR_SetDuty(int8_t leftDuty, int8_t rightDuty)
 {
 	leftDuty = preProcess(leftDuty, MOTOR_L);
@@ -47,13 +55,12 @@ void MOTOR_SetDuty(int8_t leftDuty, int8_t rightDuty)
 
 int8_t preProcess(int8_t duty, uint8_t motor)
 {
-	if (duty > 100)
-		duty = 100;
-	else if (duty < -100)
-		duty = -100;
-
 	if (duty >= 0)
 	{
+		if (duty > 100)
+			duty = 100;
+		else if (duty < 20)
+			duty = 20;
 		if (motor & MOTOR_L)
 		{
 			HAL_GPIO_WritePin(L_FORWARD_GPIO_Port, L_FORWARD_Pin, GPIO_PIN_SET);
@@ -67,6 +74,10 @@ int8_t preProcess(int8_t duty, uint8_t motor)
 	}
 	else
 	{
+		if (duty < -100)
+			duty = -100;
+		else if (duty > -20)
+			duty = -20;
 		if (motor & MOTOR_L)
 		{
 			HAL_GPIO_WritePin(L_FORWARD_GPIO_Port, L_FORWARD_Pin, GPIO_PIN_RESET);