REGISTER | LOGIN
Home    Bloggers    Blogs    Article Archives    Messages    About Us   
Tw  |  Fb  |  In  |  Rss
Signal Chain Basics

Signal Chain Basics #128: Optimizing solenoid control with precision current measurement

Dan Harmon
DHarmon
DHarmon
9/15/2017 3:56:33 PM
User Rank
Newbie
Re: solenoid position
Thanks for reading and highlighting your patent. Regards, Dan

50%
50%
DHarmon
DHarmon
9/15/2017 3:55:35 PM
User Rank
Newbie
Re: The current in a solenoid does not control its position...
Thanks Hugh for clarifying and adding to my article. Regards, Dan

50%
50%
steve.taranovich
steve.taranovich
9/13/2017 4:03:14 PM
User Rank
Blogger
Re: The current in a solenoid does not control its position...
Readers can enter this link into their browser for the patent page https://www.google.com/patents/US6249418

50%
50%
steve.taranovich
steve.taranovich
9/13/2017 4:01:16 PM
User Rank
Blogger
Re: The current in a solenoid does not control its position...
@HughVartanian--thanks for you excellent addition to this topic

50%
50%
forthprgrmr
forthprgrmr
9/13/2017 10:11:12 AM
User Rank
Newbie
solenoid position
I did this 18 years ago. See my (now expired) patent: US6249418 - easy to look up but PlanetAnalog won't let me include a url to the page. Yes you can get position by measuring the current and modelling the current/flux relationship. Not perfect, but very good.

50%
50%
HughVartanian
HughVartanian
9/13/2017 9:11:11 AM
User Rank
Newbie
The current in a solenoid does not control its position...
The author suggests that by controlling a solenoid's current one can directly infer and control its armature's position. This is something of a misrepresentation. The current through a solenoid coil is directly proportional to the magnetic field generated which is generally related to the force on the armature and is only loosely related to the position of the armature. In fact in all of the solenoids, that I have experience with, the relationship between the force and the current (& induced magnetic field) depends on the size, position and magnetic properties of the armature relative to the coil. If one has a force applied against the armature with, say, a spring, then one could do a manageable job plotting the position vs. current (& magnetic field). It certainly isn't going to be linear, particularly if the force is not constant vs position. The relationship is certainly subject to any number of variables (spring constant, mechanical and physical property variations, etc.) This may all add up to make the open loop control of the position vs current suitable for a given application, but eyes need to be wide open between the requirements and the capability of the use of the current to control position. Certainly, to make a control system that controls position with a position and velocity feedback control system, one requires a good current control loop actually driving the solenoid (or motor, whatever electromagnetic actuator). To implement a current control loop, one does need fast (10x the velocity loop bandwidth is a good place to start) and accurate feedback of the load current. That way it can respond to current commands generated by the outer control loops to get that solenoid to where it needs to go. (if one uses a permanent magnet instead of a plain iron bar, and bidirectional current feedback/control, one can move the armature in both directions!!!) (different chip needed, I believe) -Hugh

50%
50%
More Blogs from Signal Chain Basics
Despite this reputation, I2C does have its challenges: a limited number of bits for a unique address can create address conflicts, or multiple devices may require different input voltages. Although solving these problems may seem straightforward, there are implication challenges to consider
High-speed data converters now digitize or generate signals directly at radio frequencies up to several gigahertz, replacing traditional radio-frequency (RF) components like mixers, local oscillators (LOs) and amplifiers. This article focuses on the transmitter (downlink) using an RF sampling digital-to-analog converter (DAC); my next article will cover the receiver (uplink)
Some applications require the production of multiple clocks with a synchronous, adjustable phase. Many single-chip semiconductor solutions can accomplish this for low frequency applications
flash poll
educational resources
 
follow Planet Analog on Twitter
Planet Analog Twitter Feed
like us on facebook
our partners
Planet Analog
About Us     Contact Us     Help     Register     Twitter     Facebook     RSS