Lecture 23 Dimitar Stefanov Wheelchair kinematics Recapping Rolling
- Slides: 19
Lecture 23 Dimitar Stefanov
Wheelchair kinematics Recapping Rolling wheels Instantaneous Centre of Curvature (ICC) motion must be consistent Nonholonomic constraint
Position Estimation (xn+1, yn+1) (xn, yn) Basic position estimation equations are: where: D = vehicle displacement along path; Θ = vehicle orientation (heading).
Ackerman Steering • The inside front wheel is rotated slightly sharper than the outside wheel (reduces tire slippage). • Ackerman steering provides a fairly accurate dead-reckoning solution while supporting traction and ground clearance. • Generally the method of choice for outdoor autonomous vehicles.
Ackerman Steering (cont. 1) Θo Θi Ackerman equation: where: Θi = relative steering angle of inner wheel; Θo = relative steering angle of outer wheel; l = longitudinal wheel separation; d = lateral wheel separation.
Ackerman Steering (cont. 2) Θo ΘSA Θi ΘSA = vehicle steering angle.
Synchro Drive • Three or more wheels are mechanically coupled. All wheels have one and the same orientation and rotate in the same direction at the same speed. • Improved dead reckoning. • Synchro drives use belt, chain or gear drives. • Problems in steering accuracy with wear/tear
Synchro Drive Dead reckoning for synchro-drive:
The MECANUM wheel (concept)
Tricycle • If a steerable drive wheel and encoder is used, then we can use the Ackerman steering model. • Otherwise use we the differential odometry mode
Tricycle Problems • When going uphill the center of gravity of the wheelchair tends to move away from driven wheel. Causing loss of traction. • As Ackerman-steered design causes surface damage.
Omni-Directional Drives • Minimum is a 3 wheel configuration. • Each individual motor are driven independently, using velocity control.
Omni-Directional Drives, continue Let’s note the velocity of the wheelchair platform in x and y direction with Vx and Vy respectively.
Beacon-based Localization • Trilateration – Determine wheelchair position from distance measurements to 3 or more known beacons. • Triangulation – Determine wheelchair position for angular measurements to 3 or more known beacons.
Triangulation • Solution to constraint equations relating the pose of an observer to the positions of a set of landmarks. • Usually, the problem is considered in the 2 D case.
Triangulation • Passive • Active triangulation (AT): -A controlled light source (such as a laser) is positioned at point P 1. -A imaging detector is placed at P 2. -The distance A is preliminary known. -The image detector measures the angle position of the reflected-light beam. • AT requires one camera or one position sensitive detector; • AT does not depend on the ambient lighting of the object.
Active triangulation Photo detector – one- or two-dimensional array detector such as a CCD camera or photosensitive line. Calibration – signals are measured on two preliminary known distances between the sensors and the object.
Active rangefinder chip – an example TRC Beacon navigation System
Light guidance system, Dohi Lab, Japan
- Dimitar sasselov
- John nochev
- Dimitar obshti
- Aplusphysics kinematics-horizontal kinematics
- Konstantin stefanov
- Polarni dijagram
- Difference between flat rolling and shape rolling
- Rolling
- Hot rolling vs cold rolling
- Hot rolling
- Zipper cracks in rolling
- 01:640:244 lecture notes - lecture 15: plat, idah, farad
- One handed wheelchair
- Wheelchair backrest for scoliosis
- Wheelchair rugby murderball
- Olectanon
- Fire safety for wheelchair users
- Modulus of elasticity
- Atp wheelchair evaluation
- Chapter 15 scalp care, shampooing, and conditioning