Some people would argue that a remote controlled robot is not a robot. When you get into the design and actually getting it to work, however, it can be just as tricky as an autonomous robot. Remote controlled robots are far more practical for some tasks, especially when the user's senses and judgement are superior to the robot's potential sensing ability. A remote controlled LEGO robot works very similarly to an autonomous one, except that the user is directly triggering the sensors to activate routines in the robot's program.

There are four ways to remotely control LEGO robots as far as I can tell.

1. There is the Mindstorms remote, which works fine as long as you're the only robot around, but has limited infrared transmition. You can use the remote to trigger programs, control motors, and trigger programs. I see the remote's best use is to test if a robot can actually move or turn.
2. You can control the robot via the infrared tower using programs on your PC. There are multiple ways to do this. This requires your tower to be in range of the robot, and it has to be wired to your computer.
3. You can build a tethered robot. Using sensors that you hold, you attach wires directly to the imput ports on the RCX. The wires limit the mobility of the robot, but this virtually gaurantees that the robot will receive input from the sensors.
4. You can build a remote control using an RCX and sensors to remotely control a robot with an RCX and outputs,such as motors. The RCX has the ability to send number coded messages via infrared, and these messages can be interpreted by another RCX to activate routines.

I have experience in the last two methods. Here a few ideas and examples to help you build your own remote controlled robot.

An example Remote Controller. Uses an angle sensor and two touch sensors to send signals to the robot. This design uses the rotation sensor for left-right and the touch sensors for forward-back.

The design below uses two touch sensors activated by two joy sticks. The program for this robot allows it to go left, right and forward. clever programming could allow you to make the robot go backwards also.

Here's an example program for this robot:

Strobe

Strobe was designed to compete in the Robotics Society of America's Spring Robot Games. It won first place in Mini Remote Sumo. Strobe's design is fairly simple, it's basically a box with wheels. It uses four motors, providing it with a lot of power. It's speed was a bit difficult contol, especially in turns. I solved this problem by having the motors pulse. They turn for 5 hundredths of a second and pause for the same amount of time. This made for very precise rotation and made Strobe fun to drive- especially when it could push around objects many times its own mass.

See the video of strobe in action: Mini Sumo

Strobe's Controller uses a rotation sensor dial for forward and back. The way I set it up, negative values on the rotation sensor triggered forward movement, positive values, reverse, and the touch sensors trigger pulsing to the left and right.

I used a coat hanger to suspend the wire above the robot, and duct tape to hold it together.

CLICK HERE to see a full size picture of the Strobe Robolab Program