Canards are very dangerous, but if used properly, help the pilot.
As Luke mentioned, it improves stability, just like D Powers video did with his high alpha setup and gyro.
One way it helps, is assisting in the pitch axis. I fly a F-22 EDF with TV plus working canards. As the battery voltage goes down when doing high alpha's and slow flight, the upward thrust lessens and sometimes the nose will not go over and it just slogs along. Added canards, now problem is solved. It pitches the nose over(rather than a stall) and the EDF gathers speed to fly.
After a number of runs, I fly with TV and functioning canards at all times.
The key--set the angles properly-- mine is nose down 45 degrees with 50 % expo and 14 degrees nos up with 15% expo. This is mixed in with elevator travel.
The reason for high expo is when I put nose down for landing, very little canard is used. And yes, it took a number of crashes to get everything resolved.
The second way it is used is to improve the lift characteristics as you approach the stall angle. If properly located, on average, the stall angle is increased 10-15 degrees(Nasa's numbers) and the canard movement is small(+/- 5 degrees). Go watch a Grippen landing, that will show it is done. Oh yeah, they now use the canard as an airbrake!!
I have taken a F-22 and added canards to do testing with a prop setup. Notice as I said before, if properly located, it will increase the stall angle. What is the formula? Research shows:
canard shape, size, distance from wing, distance above/below/equal wing, wing shape/design,airspeed,deflection and many other factors control it. So change one factor slightly and there has to be a way before/after to show the results. It is like a shot in the dark.
One reason, not to much testing is being done by Nasa and companies is that they are designing's planes to reduce the radar signature and canards don't help.
So, if you are going to use them, be prepared for a lot of unexpected's.
I like to design and fly unique planes.