Thank you for your reply. Oh, I didn't write OpenCat.ino. Maybe,that's the cause of this trouble.

When he tries to walk at normal speed, he loses his balance.

@Rongzhong Li Thank you. I can calibrate Nybble and the cat can move.

The first half of the video shows the situation before and after the start of calibration. The second half of the video is an operation check after writing Nybble.ino. At the end of the video, Nybble tries to walk with knees and elbows. Nybble abnormal actions

Hello. Maybe I was able to calibrate ,Maybe. But Nybble can't walk normally and the cat try to walk with his elbows.And also Nybble can't make 'rest' posture.

Hello. Sorry I understand 'd'. After I typed 'd' , the cat stretched out using the whole body. But Maybe the cat can't "kbalance". The cat poses as if the cat stood with knees and elbows. Is "kbalance" action this pose? After I upload Nybble.ino and the robot beeps and stops movement every time.

I retried again after connecting BATT and V_S. After I type 'd' and the cat move.But serial monitor show 'shut down servos' after the cat's move. And the cat didn't move. Is the adjustment of the leg part quite delicate?

I retry after connecting jumper wire SW3 between BATT and V_S. And Maybe I could calibrate. I typed 'd' and Nybble moved. But Nybble couldn't do 'kbalance' So, I reconnected jumper wire SW3 between V+ and V_S . But Nybble can't move normally and yellow LED was blinking. Is this cause lithium ion battery?

Hello. Thank you for your reply. I use an unknown battery as external power supply. I live in Japan. I read "Report your battery'. But maybe , I can't buy batteries from walmart.(Maybe I can't bought batteries from USA. Lithium ion batteries may ignite and air transport is prohibited. ) So I was looking for “14500 3.7V li-ion battery unprotected” . But I found this one as battery to get easily. I bought the battery at the following website. https://item.rakuten.co.jp/surprise-collection/14500-2-800/?s-id=ph_pc_itemname But I don't know the manufacturer of this battery.