Lect 24 Flashcards
What are the properties of measurement systems?
What is accuracy repeatability stability of measurements?
Accuracy: capability of a sensor to have measures close to real values
Repeadability: Capability of reproducing an output similar, over repeated measurements of the same input quantity
Stability: capability of keeping the same measuring characteristics over time/temprature
What is linearity error offset error and resolution error?
Linearity error: If you have linar changes in the input, is it true that you will get a linear change on the output
Offset error: Value of a measured output for a zero input
Resolution error: Min change in the input that you can accept
What are motor encoders?
Sensor attached to the shaft of the motor. It measures the position or the speed of the wheels or steering
What are heading sensors?
They are used to determine the robots orientation and inclination.
Can be proprioceptive: Gyroscope, acceleration
or exteroceptive: compass, inclinometer
With an appropriate velocity information, to integrate the movement to a position estimate : DEDUCED RECKONING(estimate the position by measuring the movement)
They are important because we can use them to integrate over time in order to extract the velocity we can estimate the position
What is deduced reckoning and why is it dangerous to move in deduced reckoning?
Deduced reckoning is integrating the movement(motion) in order to find the final position.
It is very dangerous because, while integrating the movement we also integrate the errors. These errors can be very high and it can bring you to rocks in the sea
What is compass and what is the cross sensitivity(talking)
Compass is measuring the magnetic field. But it can sense all kind of magnetic fields, therefore it will be affected by also the magnetic field of earth. Which is called as cross talking.
What is gyroscope?
Heading sensors that keep the orientation to a fixed reference frame. Two categories: Mechanical and optical.
Mechanical gyroscope:
You can move the structure of gyrosopce in any directions and the wheels is keeping the angular momentum
1)standard gyro(angle)
2) rate gyro(speed) -> you need to reset gyroscope from time to time
Optical Gyroscope:
1)Rate Gyro(speed)
What is accelometer?
There is a seismic mass, it shifts along the direction the mass is moving in the direction of linear acceleration.
It can be dynamic, static(inclometer),airbag sensors
Piezoelectric accelerometer: senses pressure and you can find hw much mass is accelerating: vibration analysis earthquake sensors.
What is IMU?
Inertial Measurement Unit
A closed system for detecting the orientation and motion of a vehicle or a human.
Consists of: 3 accelometers, 3 gyroscopes, 3 magnetometers.
*** You can start from position zero and you do a certain motion, and the processing f data coming from those 9 sensors can reconstruct the trajectory of the object.
Very reliable for short amount of time. but when you do integration for long time, you have a bigger drift because you also integrate the errors. Everytime you make a small error, this error will accumulate in final acceleration. You need to correct the drifts with additional measurements.
What are contact sensors?
Passieve
Cheap
Poor sensitivity
Poor localization
Tactile sensors?
Measure contact with the objects. Sensors that senses the touch.
Touch sensors: have switched
Bumper sensors: Springs and contacts, understands from which side it is going to collide
What is roboskin concept?
The sensing is not based on the switches now, it is based on electronic sensing with capacitors. By measuring the difference on capacitors, we can estimate something happened and if we calibrate we can estimate the force applied to the sensor.
