Individual or paired arm control in a wellbore tractor

An independent or paired arm control system configured for a wellbore tractor configured to be run in a borehole penetrating a formation, the control system comprising:

• a 3-port/2-way normally open solenoid valve arranged in a drive module of the wellbore tractor, the drive module having at least one arm with at least one wheel or belt,
• a hydraulic cylinder-piston assembly comprising a hydraulic cylinder (with an actuator piston and a retraction spring, arranged therein, the hydraulic cylinder-piston assembly arranged within the drive module,
• hydraulic pressure line connected to a hydraulic pump configured to provide high pressure by means of a hydraulic fluid,
• a return hydraulic line connected to a reservoir configured for containing the hydraulic fluid,
• a control port-S of the 3-port/2-way normally open solenoid valve is connected to the hydraulic cylinder of the hydraulic cylinder-piston assembly, a return port of the 3-port/2-way normally open solenoid valve is connected to the return hydraulic line, and a pressure port of the 3-port/2-way normally open solenoid valve is connected to the hydraulic pressure line.