This article presents a PID control system for a lower-limb rehabilitation robot that not only features satisfactory control performance for pedal angle but also provides us with the function of pedal torque estimation. A PID controller guarantees that the pedal angle tracks a reference trajectory. The integration of the equivalent-input-disturbance (EID) approach in the control system precisely estimates pedal torque in a real-time fashion. And the method achieves safety monitoring by detecting abnormal torque variations such as those caused by spasms or excessive effort. Simulation results and comparisons with active disturbance estimation methods validate the effectiveness of the method.