Tham khảo tài liệu 'anatomy of a robot part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 186 CHAPTER SEVEN What Types of Brakes Exist Remember the general definition. Brakes are a method of slowing down or remaining in place . This is a function that can be implemented in the following ways No brakes Okay we ve all had bicycles like this. The truth is aside from scraping shoes on the ground it s possible to slow down just by coasting to a stop. This does not work real well going downhill but it works just fine on level ground and going uphill. Even if the robot has great disk brakes the control software should be smart enough to recognize when they don t need to be used. This sort of braking action consumes very little energy but it requires rather sophisticated software. Here s an example of the type of software action that could save energy. Suppose the robot must move 4 feet. Suppose from experience the robot knows it will coast 2 feet once the robot is at top speed and the motor is turned off. It s likely that the least energy-expending method of moving is to get to top speed move for 2 feet turn off the motor and coast for 2 feet until the robot comes to a stop. Other power expenditure plans may work better but certainly little power will be wasted in the last half of the journey. The motor and the brakes will both be off. One thing is for sure though. The robot will not complete the move in the minimum amount of time. Motor braking Just as a motor can be used to accelerate a robot so too can it be used to decelerate. Motors can be used as brakes in a couple of different ways. Because moving coils of wire through magnetic fields cause a current to flow some motors become generators when the rotor is spun around. If the motor coils are shorted out then a larger current will flow and the motor will resist the spinning motion on the rotor. By definition this causes braking. More sophisticated motor control circuits are available that can brake more effectively by driving the motor coils in an optimum fashion. In fact the motor can be partially driven
