Choose a distance sensor and how to connect it?

Question

Arduino

Hello.
Given:
1. A robot on a wheeled chassis for indoors is not too big - no more than half a meter in any dimension (although the sensor can be taken out higher in height).
2. On board the robot is a netbook that is powered by a battery
3. It is assumed that the robot can move around in a room where there is furniture, people and animals.
4. For the movement of the robot, sensors (one or more) are needed, which must solve the following problems:
4.1. do not bump into fixed objects and walls
4.2. not run into people
4.3. do not run into animals, including those covered with wool.
4.5. do not fall down the stairs
Question:
1. How many and what kind of sensors do you need?
2. At what height is it better to fix them?
3. How best to pair them with a computer?
4. What software is needed in this case?
ps a more budget solution is better than a laser rangefinder.
pps the netbook has a camera, but it seems to me that this is not a very convenient tool in this case

Answer 1

HC-SR04 Distance Sensor for example. Ultrasonic.

Answer 2

The dimensions of the robot and the processing power allow it to be used as a Kinect sensor.

Answer 3

US + kinect