Recon Outdoors Talon IR Spécifications télécharger pdf (Page 59)

Motor Control

Figure 3.1 PWM signals and transmitted power (a) 50% (b) 90% (c) 10%

The integration of a digital controller in the motor driver has the added advantage of

separating the timing critical motion control algorithms (PWM generation) from the

higher level robot software. This is particularly important when a non-real-time

operating system such as Microsoft Windows XP is used where process timing cannot

be guaranteed constant.

PWM signals cannot directly control the motors therefore a power converter is

required and the most common form of switching motor driver is the H-Bridge

topology illustrated in Figure 3.2. Four switching devices are connected to provide

four quadrants of DC motor operation, driving and breaking in both the forward and

reverse directions.

Figure 3.2 H-Bridge switching topography

The H-bridge works by directing the motor current in a certain path by manipulating

the four switches S1 – S4. Forward motion is achieved by turning on switches 1 and 4

with 2 and 3 off. Likewise, when 2 and 3 are on and 1 and 4 are off, the motor rotates

in the reverse direction. Braking can be achieved by opening the high side (S1 S3)

switches and closing the low, thus creating a feedback loop through the motor and

ground.

Motor

Vcc

(a)

(b)

(c)

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Recon Outdoors Talon IR Spécifications Page 59