1.Rack and pinion device
Usually, the rack is fixed. When the gear is driven, the gear shaft and the carriage move linearly along the direction of the rack. In this way, the rotational motion of the gear is converted into the linear motion of the carriage, as shown in Figure 1. The carriage is supported by guide rods or guide rails. The device has a large hysteresis.
Figure 1 Rack and pinion device
2. Ordinary screw
Ordinary screw drive is a rotating precision screw that drives a nut to move along the screw axis. Because ordinary screws have large friction, low efficiency, and large inertia, they are prone to crawling at low speeds, have low accuracy, and have large hysteresis, so they are rarely used on robots.
3.Ball screw
Ball screws are often used on robots because their friction is very small and their motion response is fast. Since the ball screw places many balls in the spiral groove of the screw nut, the friction experienced during the transmission process is rolling friction, which can greatly reduce the friction, so the transmission efficiency is high and the crawling phenomenon during low-speed movement is eliminated. Applying a certain preload force during assembly can eliminate backlash.
As shown in the figure 2, the balls in the ball screw come out of the steel sleeve, enter the ground guide groove, and return to the steel sleeve after turning 2 to 3. The transmission efficiency of the ball screw can reach 90%, so only a very small driving force is needed and a smaller driving connector is used to transmit motion.
Figure2 Ball screw pair
(Source: Robot Network)