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Actuators & Drivers
The H-Bridge block represents an H-bridge motor driver. The block has the following two Simulation mode options:
PWM — The H-Bridge output is a controlled voltage that depends on the input signal at the PWM port. If the input signal has a value greater than the Enable threshold voltage parameter value, the H-Bridge output is on and has a value equal to the value of the Output voltage amplitude parameter. If it has a value less than the Enable threshold voltage parameter value, the block maintains the load circuit using a freewheeling diode and one of the bridge switching devices. The signal at the REV port determines the polarity of the output. If the value of the signal at the REV port is less than the value of the Reverse threshold voltage parameter, the output has positive polarity; otherwise, it has negative polarity.
Averaged — The H-Bridge output is
where:
VO is the value of the Output voltage amplitude parameter.
VPWM is the value of the voltage at the PWM port.
APWM is the value of the PWM signal amplitude parameter.
IOUTis the value of the output current.
RON is the Bridge on resistance parameter.
The model is based on the following assumptions:
Set the Simulation mode parameter to Averaged to speed up simulations when driving the H-Bridge block with a Controlled PWM Voltage block. You must also set the Simulation mode parameter of the Controlled PWM Voltage block to Averaged mode. This applies the average of the demanded PWM voltage to the motor. The Averaged mode assumes that the effect of the motor inductive term is small at the PWM frequency. To verify this assumption, run the simulation using the PWM mode and compare the results to those obtained from using the Averaged mode.
You can only linearize the H-Bridge block when you set the Simulation mode parameter to Averaged.
Threshold above which the voltage at the PWM port must rise to enable the H-Bridge output. This parameter is only used when the Simulation mode parameter is set to PWM. The default value is 2.5 V.
The amplitude of the signal at the PWM input. The H-Bridge block only uses this parameter when the Simulation mode parameter is set to Averaged. The default value is 5 V.
When the voltage at the REV port is greater than this threshold, the output polarity becomes negative. The default value is 2.5 V.
When the voltage at the BRK port is greater than this threshold, the H-Bridge output terminals are short-circuited. The default value is 2.5 V.
The amplitude of the voltage across the H-Bridge output ports when the output is on. The default value is 12 V.
The type of output voltage can be PWM or Averaged. The default mode, PWM, produces a pulse-width modulated signal. In Averaged mode, the output is a constant whose value is equal to the average value of the PWM signal.
The total effective resistance of the semiconductor switches that connect the motor to the two power rails when the voltage at the PWM port is greater than the Enable threshold voltage. The H-Bridge block assumes synchronous bridge operation where the load is connected via one of the freewheeling diodes and one of the bridge switching devices. To use a second bridge switching device instead of the freewheeling diodes, set the Freewheeling diode on resistance value on resistance to half of the Bridge on resistance value. The default value is 0.1 Ω.
The total resistance in the freewheeling diodes that dissipate the current that flows through the motor when the voltage at the PWM port is less than the Enable threshold voltage. The default value is 0.1 Ω.
The block has the following ports:
Positive electrical output voltage.
Negative electrical output voltage.
Pulse-width modulated signal. The voltage is defined relative to the REF port.
Floating zero volt reference.
Voltage that controls when to reverse the polarity of the H-Bridge output. The voltage is defined relative to the REF port.
Voltage that controls when to short circuit the H-Bridge output. The voltage is defined relative to the REF port.
See the Controlled DC Motor, Linear Electrical Actuator (System-Level Model) and Linear Electrical Actuator (Implementation Model) demos.
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