Most joysticks have build-in springs to give a return to center force. Hardly realistic, since the centering force stays constant regardless the flight conditions.
I have bought a commercial force-feedback stick, (Logitec Wingman 3D
Force Feedback) that showed some improvement, as there is some relation between
centering force and airspeed. Also gear and landing bump jolts were
incorporated. The main drawback of the commercial FF sticks is the rather
low force, and the apparent delay between stick movement and force response.
To improve the stick force, I hacked the FF stick, and used the FF signals
to drive power buffers with bigger motors. This is described in
Hacking a Force Feedback Stick.
MS Sidewinder Force Feedback 2 stick can also be successfully hacked: see
MS Sidewinder FF2 hacking page
The force feedback added to a flight yoke is described in
Flight yoke FF mechanics
A second generation flight yoke with force feedback is described at Force Feedback Yoke II page.
The force feedback added to a flight stick is described in Flight stick
DIY force feedback interfacing describes the DIY method of making control forces depend on flight parameters.
Rudder pedal forces also depend heavily on flight conditions. With the
new interface possibilities that I discovered with the
motion platform projects, I now
also had a way of adding force feedback on rudder pedals.
The force feedback added to rudder pedals is described in
Rudder pedals FF mechanics