I have a DC motor, which is used as an electromagnetic brake. However I want to leave certain frequencies uninhibited, so I thought this should be possible by adding a shunt filter on the DC motor mains. The Idea is that if I high-pass the current through the shunt, that for a sinusoidal velocity input below 3 Hz no current flows through the motor coils resulting in no back-emf torque.
The circuit below consists of a sinusoidal voltage source as a result of the emf of the DC motor, the armature inductance (L1) and resistance(R1) and a still unresolved shunt circuit across the actuator leads.
What I want to accomplish with the shunt is to obtain a certain frequency response of the current in the shunt circuit, but I'm struggling with the design. Most of what I've found describes voltage filtering behaviour and I'm wondering if it's possible to filter the current in a shunt circuit.
The schematic currently shows a low pass filter arrangement, which in my understanding will result in a high current for high frequencies and a low current for low frequencies as the capacitor will have a low and high impedance respectively. The inductor acts as a low pass filter on the current, but it's filtering higher frequencies I don't really care about.
What I would like to achieve is a frequency response somewhat like the picture below. The important part is the relatively close proximity of pass and stopband frequencies.
I would like to know if it is possible to obtain such a filter on the total current and whether this could be done without any need for active control (aside from opamps and "dumb" active components)