A brushless DC motor has a motor constant K_t = 0.1 N·m/A and is geared with a 100:1 gearbox (output torque = 100 × motor torque). If the motor can deliver a peak current of 10 A, what is the maximum torque at the gearbox output?
A1 N·m (motor torque only)
B10 N·m (motor torque with current)
C100 N·m (motor torque with gearbox)
D1000 N·m (motor torque with gearbox and current)
Quantization in feedback systems is particularly problematic for PID control because the integral term can accumulate error and build up commands that oscillate at the quantization frequency. This is why encoder selection is important for precision robot control: a coarse encoder (256 CPR) may oscillate noticeably, while a fine encoder (16,000+ CPR) effectively eliminates quantization issues within the control bandwidth.
Question 2 True / False
A servo hydraulic actuator used for a high-load robotic manipulator has response time of 50 ms (the time from command input to 90% of peak output). When computing a feedforward controller that predicts the required command for a desired trajectory, this actuator lag must be accounted for. True or false?
TTrue
FFalse
Answer: True
This trade-off is fundamental. You cannot have both high speed and high torque from a small motor. Robots exploit this by using high-ratio gearboxes to compress the motor's power into low-speed, high-torque outputs suitable for manipulation. Without gearboxes, robot joints would need enormous motors to produce adequate torque, making robots heavy, expensive, and inefficient.