As the speed of automation goes high, engineers need high speed gear interlocks. I stumbled upon this demonstration on Youtube about new technology developed by Mitsubishi Electric company that allows for interlocks at speed as high as 6000 RPM! Unbelievable isn't it? The demonstration below shows seamless engagement of gears at about 4500 rpm. Check -

The motors in each unit are controlled using single, multi-axis servo amp. Once time-synchronised, the braking energy of one axis can be utilised to power the next gear; reducing the overall energy usage. I'm not sure about mechanisms Mitsubishi engineers have developed that allow precise control over the motor speeds. But what we see here is surely impressive.