diff --git a/BallCamera.go b/BallCamera.go
index 4effbbb..29d2753 100644
--- a/BallCamera.go
+++ b/BallCamera.go
@@ -187,6 +187,9 @@ type PTZ struct {
 }
 
 func (this *BallCamera) GetPTZ() (PTZ, error) {
+	if this == nil {
+		return PTZ{}, errors.New("BallCamera is nil")
+	}
 	if this._type == BuKongQiu {
 		var data PTZ
 
@@ -273,6 +276,9 @@ func padding(n int) ([]byte, error) {
 }
 
 func (this *BallCamera) PtzGotoPut(Action int, P, T, Z float64) error {
+	if this == nil {
+		return errors.New("BallCamera is nil")
+	}
 	if this._type == BuKongQiu {
 		SerialStartHandle, err := Core.SerialStart(this.userId, func(lSerialHandle Core.LONG, lChannel Core.LONG, pRecvDataBuffer []byte, dwBufSize Core.DWORD, pUser unsafe.Pointer) {
 		})
@@ -400,7 +406,9 @@ func (this *BallCamera) retrySend(handle Core.LONG, cmd []byte, maxRetries int,
 }
 
 func (receiver *BallCamera) StartBus(direction int, speed int) error {
-
+	if receiver == nil {
+		return errors.New("BallCamera is nil")
+	}
 	err := Core.PTZControlWithSpeed_Other(receiver.userId, Core.LONG(receiver.deviceInfo.ByStartChan), Core.DWORD(PTZEnum.toHikPTZEnum(direction)), Core.DWORD(0), Core.DWORD(speed))
 	if err != nil {
 		return err
@@ -408,6 +416,9 @@ func (receiver *BallCamera) StartBus(direction int, speed int) error {
 	return nil
 }
 func (receiver *BallCamera) StopBus(direction int, speed int) error {
+	if receiver == nil {
+		return errors.New("BallCamera is nil")
+	}
 	err := Core.PTZControlWithSpeed_Other(receiver.userId, Core.LONG(receiver.deviceInfo.ByStartChan), Core.DWORD(PTZEnum.toHikPTZEnum(direction)), Core.DWORD(1), Core.DWORD(speed))
 	if err != nil {
 		return err
@@ -429,9 +440,15 @@ func verify(data []byte) (byte, error) {
 }
 
 func (this *BallCamera) Logout() error {
+	if this == nil {
+		return errors.New("BallCamera is nil")
+	}
 	return Core.Logout(this.userId)
 }
 
 func (this *BallCamera) Status() bool {
+	if this == nil {
+		return false
+	}
 	return Core.NET_DVR_RemoteControl(this.userId)
 }