diff --git a/app/by_stepper.c b/app/by_stepper.c
index 35fabc0..58a6497 100644
--- a/app/by_stepper.c
+++ b/app/by_stepper.c
@@ -76,6 +76,10 @@ void by_stepper_set_position_millimeter(float distance)
       return;
     }
 
+    if (distance > 170) {
+      distance = 170;
+    }
+
     gpio_bits_write(GPIOA, GPIO_PINS_9, FALSE); // EN
     position_aim    = (int64_t)(distance * ENCODER_PULSE_PER_MILLIMETER);
     position_offset = position_aim - position;
@@ -87,7 +91,10 @@ void by_stepper_add_position_millimeter(float distance)
 {
   if (!running_flag) {
     gpio_bits_write(GPIOA, GPIO_PINS_9, FALSE); // EN
-    position_aim    = position + (int64_t)(distance * ENCODER_PULSE_PER_MILLIMETER);
+    position_aim = position + (int64_t)(distance * ENCODER_PULSE_PER_MILLIMETER);
+    if (position_aim > 170 * ENCODER_PULSE_PER_MILLIMETER) {
+      position_aim = 170 * ENCODER_PULSE_PER_MILLIMETER;
+    }
     position_offset = position_aim - position;
     running_flag    = 1;
   }
@@ -121,7 +128,7 @@ void by_stepper_init(void)
   while (gpio_input_data_bit_read(GPIOB, GPIO_PINS_10) == SET) {
     gpio_bits_write(GPIOA, GPIO_PINS_8, by_stepper.dir ? TRUE : FALSE);                    // DIR
     gpio_bits_write(GPIOB, GPIO_PINS_15, !gpio_output_data_bit_read(GPIOB, GPIO_PINS_15)); // CLK
-    DWT_Delay(40U * (uint16_t)by_stepper.speed);
+    DWT_Delay(30U * (uint16_t)by_stepper.speed);
   }
 
   position        = 0; // 位置归零