Mixer drum drive with variable displacement motor

A vehicle comprising:

• an engine;
• a mixing drum;
• a drum drive system including:
• a variable displacement pump selectively mechanically couplable to the engine such that a pump speed of the variable displacement pump is based on an engine speed of the engine;
• and
• a variable displacement motor fluidly coupled to the variable displacement pump such that a motor speed of the variable displacement motor is based on a flow of a fluid received from the variable displacement pump, wherein the variable displacement motor is configured to drive the mixing drum at a target drum speed;
• and
• a controller configured to selectively control the engine, the variable displacement pump, and the variable displacement motor to provide the target drum speed, wherein the target drum speed is based on an input from an operator of the vehicle, and wherein to provide the target drum speed, the controller is configured to:
• (i) initially operate the variable displacement motor at a maximum motor displacement and operate the variable displacement pump at a pump displacement that provides the target drum speed without needing to actively manipulate the engine speed;
• (ii) increase the pump displacement and decrease a motor displacement without needing to actively manipulate the engine speed while still providing the target drum speed;
• and
• (iii) increase the engine speed in response to the pump displacement reaching a maximum pump displacement and the motor displacement reaching a minimum motor displacement if necessary to maintain the target drum speed.