Modification of 55 V DC motor control with counter-current braking

Modification of an existing 55 V DC motor control system

I have an existing circuit for controlling a 55 V DC motor. The circuit needs to be modified to include an automatic plugging (counter-current braking) function.

The existing relay logic should be retained as much as possible.

1. Existing circuit
Supply: 55 V DC

Current components:

DC motor
2 PWM controllers
4 relays for reversing the direction of rotation
S1 = Winding in
S2 = Unwinding

Desired change:
One PWM controller is to be completely eliminated.
The PWM2 controller previously used for S2 is no longer needed and should be removed from the circuit entirely.
Only PWM1 remains (for S1 / winding in).
The reason for this is that the motor is to be operated directly at 55 V during unwinding. The unwinding speed is already sufficiently high and should not be reduced via PWM.

This results in the following configuration:
S1 / Winding in:
→ PWM1
→ Adjustable, slower speed

S2 / Unwinding:
→ Direct 55 V supply, without PWM

2. Desired counter-current braking

During unwinding, the motor runs at high speed.
When S2 is released, the motor should not simply coast to a stop.
Instead, the winding-in direction (via S1) should be automatically activated for a brief period.
This is intended to bring the motor to a standstill very quickly through counter-current braking.
Technically, the counter-current braking is to be achieved by activating the winding-in direction for a short time.

3. Time-delay relay / Pulse function

A solution is required that generates a single, brief pulse when S2 is released. Preferred function: Single shot / Trailing edge / Falling-edge triggered pulse
The pulse should initially be set to approximately 100 ms.

Ideally, the pulse duration should be adjustable—for example, within the 50–500 ms range.
This allows the optimal braking time to be determined empirically at a later stage.
Additionally, a brief dead time between the deactivation of S2 and the counter-current pulse would be desirable. Target: approx. 20–50 ms.

4. Voltage
The entire system operates at 55 V DC.
A solution is preferred that:

can be operated directly at 55 V DC,
and features an output suitable for 55 V DC. If an additional relay is required for this purpose, that is also acceptable.

5. Motor power

The timing relay should not switch the motor current directly unless necessary.
The existing relay/power stage should continue to handle motor switching.
Preferably, the timing relay output should simply simulate the existing S1 control command for approximately 100 ms.

If an additional relay is required, that is not a problem.

6. Priority of S1

S1 generally takes priority.
The following behavior must be maintained:
S1 only → Retraction using PWM1

S2 only → Rapid extension using direct 55 V supply

S1 + S2 simultaneously → S1 takes priority

S2 is pressed and S1 is actuated:
→ Extension direction must be switched off
→ Followed by retraction direction

The two directions of rotation must never be active simultaneously.

7. Counter-current braking

When S2 is released, the following sequence must be strictly observed:
S2 OFF
↓
Extension direction OFF
↓
Short dead time
↓
S1 ON
↓
Approx. 100 ms
↓
S1 OFF

The dead time is essential to ensure that the two directions of rotation are not active simultaneously.

Reliable break-before-make switching must be ensured.

8. Behavior upon re-actuation of S2

After the braking pulse has finished, S2 must function normally again.
For every new extension operation, exactly one braking pulse must be generated again when S2 is released.
The pulse should not be re-triggerable while it is active.

A new circuit diagram in JPG format is required.