some LTspice draft circuits for driving a DC motor from single-phase AC line
Large DC motors such as are found in Treadmills are commonly available a less than their cost of mfgr. Sadly, their controllers are unidirectional, which prevents their use in servo systems.
High voltage DC drivers (or "amplifiers") are fantastically expensive, and require expensive DC power supplies but lamp dimmers are cheap and effective. Again, they are unidirectional.
What is needed is a bidirectional lamp dimmer for mains voltage DC motors.