TF motor is widely used in robot applications, such as joint movement, walking, various actions and so on. Aside from large robots, small robots need TF brush motor, brushless motor and TF reducer motor.
TF motor and brushless motor are commonly used for small robots. There are many brands of DC motor manufacturers in the market. In addition to foreign countries, there are tens of thousands of domestic micro DC motor manufacturers. For micro DC motor, it has complex internal structure and various parameters. For robot products, the performance of micro motor needs to be fully considered.
Under the condition of meeting the performance requirements of the robot, the price of the micro motor needs to be within an acceptable range. Under the condition that the brushless DC motor can meet, the brushless DC motor is selected. Therefore, it is necessary to consider the parameters of the TF motor as a whole and select the appropriate TF motor in combination with the requirements.
TF motor has many operating characteristic curves. For robot products, the main concerns are working voltage, speed, torque, current and size.
(1) Working motor: there may be multiple voltage parameters in the micro motor, the most commonly used is the rated voltage. TF motor can run above the rated voltage and exceed the rated speed and torque, but it cannot run for a long time, otherwise it will heat up;
(2) Rotational speed: the number of revolutions per minute of micro motor, TF motor can reach 40000 revolutions, which is quite high for micro brush motor;
(3) Torque: in robot products, a certain torque is required to complete the movement or various actions of the robot, and the unit is nm;
(4) Current: in micro motors, there are no-load current, rated current, locked rotor current, etc;
(5) Size: motor size, shaft size, section size, fixing hole size, etc.
The power supply current of the micro DC motor is DC, so the battery can be used for power supply. The size and shape of various types of micro motors are different, but most of the basic parameters have a range. The micro DC motor generally operates at high speed, but in robot applications, the output torque often can not meet the requirements, Therefore, a reducer is added to the micro DC motor to reduce the speed of TF motor and increase the output torque. TF reducer motor has the characteristics of simple use, high output torque, low speed and low noise.
In the robot Renren products, the output area with working voltage of 6 ~ 24V and 0.1 ~ 0.5nm can drive a robot of 20 ~ 30kg. For wheeled robots, the size of tires determines the maximum running speed of the robot.
The robot needs to be driven by a micro motor to move. Its speed depends on the speed of the micro motor, and the speed of the micro motor depends on the input voltage and load torque. Under the same power supply voltage, the greater the force required by the micro motor, the lower its speed and the greater the current of the micro motor. When the output reaches a certain degree, the micro motor will stall (that is, stop rotating). At this time, the current of the motor is the maximum, and the temperature of the micro motor will rise and damage the motor for a long time.
The relationship between the running speed of the robot and the rotation speed of the micro motor is v × zero point zero two × pi × W × R/60
5: Robot running speed (M / s);
W: Rotation speed of motor after deceleration;
R: Motor radius
Assuming that the average running speed of the robot is vavg, the required speed of the reduction motor is:
w=60 × Vavg/（0.02 × pi × R）
When the micro DC motor starts to supply power, the micro motor shaft has not started to rotate. At this time, the micro motor is in the locked rotor state. The maximum current of the micro motor is is. At this time, the torque generated by the motor is also the largest. Therefore, the micro motor starts to rotate. With the acceleration of the speed, the back EMF of the micro motor increases, the current and torque of the DC motor decrease, When the DC motor torque is equal to the load torque, the micro motor will reach the balance state, which is the speed of the micro motor in the balance state (the micro motor balance state refers to that the torque is equal to the load torque. In the robot, the friction climbing and acceleration factors are within the load torque).
In the application of TF motor in robot, it is necessary to consider the maximum speed that the micro motor can achieve under different load conditions. For example, under no-load conditions, TF motor can reach the maximum speed, and the no-load speed is W0. Under load conditions, the speed that can be generated when the robot motor is locked is the maximum torque, and the locked torque is ts. under other conditions, TF motor runs on the linear connection between them. If the load torque is t, the maximum speed of micro motor is w = W0 × (1-T / TS). If the maximum speed required by the micro motor is w, the maximum torque generated by the TF motor is t = ts × （1=w/w0）。
If the maximum no-load speed of the micro motor is W0 and the no-load current is I0, with the increase of load torque, the speed of TF motor is linear to the current price, and the current increases until the load torque reaches the maximum torque, and the micro motor is locked. Assuming that the torque of the micro motor continues to increase, the micro motor will be in the power generation state.
When the micro motor torque is t, the micro motor current is I = I0 + (is-i0) × T/Ts
I0: no load current;
Is: locked rotor current;
TS: locked rotor torque
According to the above, it can be concluded that the operating voltage, no-load speed, speed under a certain torque and current under a certain torque should be considered when selecting the robot reduction motor.
(1) Operating voltage: generally, the voltage of micro motor is 3VV, etc. for 12V motor, 7.2V or 9.6V power supply is generally used;
(2) Motor speed: for robot products with tire size of 5 ~ 20cm, the rated speed of micro motor ranging from 40 ~ 300rpm is sufficient;
(3) Motor torque: when calculating the torque of micro motor, generally leave 50% allowance on the basis of the above calculation. If the number of TF motors is “1”, divide the speed requirements of micro motor by the corresponding number.
(4) Current: the current determines the running time of the robot. According to the current data of TF motor, assuming that the current of micro motor is 0.01A, the motor will be too small. On the contrary, if the rated current of wechat motor is 1a, the motor will be too large.