Auto/Manual - what does it mean to you?

While replying to the Set/Reset discussion I thought about another general "how do you guys do it?" kinda question regarding Auto/Manual control.

I've seen OEMs program in either one of 2 ways...

1 - Auto or Manual (2 choices) - i.e. simple 2 position selector switch.
2 - Auto/Not Auto and/or Manual/Not Manual (4 interlocked choices) - i.e. more complex selection with momentary buttons.

I'd like to hear your opinions along with any general comments you have on what "auto/manual" means to you.

Here's my take...

Auto means just that. The machine/process does what it does all on it's own according to programming. Operator intervention may be allowed in some instances.

Manual resets all set sequencing bits and allows manual control of machine functions with the only interlocks being those which will protect against machine damage i.e. extreme overtravel limits and such. The operator becomes the control system.

Most applications that I see fall into 2 categories - either the simple Auto/Manual option that you described, or Auto/Manual/Off.

My take is that the complexity of the machine will dictate which approach is better . . .

Marc

We use a two position switch on one plc input.

Position 1, no input on plc is automatic control like you described
Position 2, input on plc is manual control like you described.

The only disccussion is if manual control is limited or not. With limited I mean for example, Motor manual on only allowed when there is no product on the conveyor. Ok, now the problems is that the photocell that 'sees' the product is damaged. The manual control will not work in this situation. So then we change the software so it will always work. The next time somebody crashes the product, now they want a limited manual control again.

My solution is:

Extra switch or button on touchscreen indication "technical control" or "smart control". Smart control checks wheter a manual action is possible or not. In technical mode everything is allowed. (Even crashing the machine). Most of the time the technical control is behind a password or uses a key.

We have a variety of mode controls depending on what is required.

Some machines/stations have a lighted momentary auto button and a stop button. When you press it once, it's in auto and the lamp lights. When you press stop, the light goes out, and the machine is in manual mode.

Other machines have a lighted auto pb, a lighted manual pb and a stop pb. The modes are mutually exclusive. (If you hit manual, it lights up and the auto mode light goes out). That gives you three modes: Auto, Manual, and Stop (in stop mode, manual functions don't work)

Other machines have an additional setup mode. It is done with a selector switch (sometimes a keyed one) which is like manual, but, some of the manual travel limitations are lifted. It also opens up data entry screens on the HMI.

Out more complicated machines have a semi-sutomatic mode. It allows the sequence to continue in auto up to predetermined points, and then stop.

We recently had to make changes to comply with safety regulations. Our strip winders would allow the operator to jog while in automatic mode. This was determined to be unsafe in our situation, so I had to take away that function.

In my experience, in manaul mode, make sure nothing happens unless the operator explicitly commands it. Like you said, "the operator is the control system.". Don't give them the opportunity to break stuff or hurt themselves, but let them have as much flexible control as possible.

Auto/Manual

We use Auto/Manual in 2 different ways, say a Auto/Manual keyswitch on the panel which dictates a fully operated plant in Auto. Manual would be for maintenance testing newly replaced equipment or to maybe return the process if possible to a fully operational state.

Individual auto / manual control would also typically be controlled from the SCADA/HMI where the approved operator can even toggle a single motor to auto or manual. I dont really like giving somebody freedom to play around while a system is running in auto.

I always like having signals high for decisions and hate assuming auto/not-auto. What if there is a line break. The system would assume it is in manual. which it is not. Thus i regard this as 2 seperate inputs.

Regards
Rheinhardt

for most machinery I've dealt with, the auto/manual is just that...auto takes the human aspect out of operation, or at least strictly limits it, and controls the process. Manual means the operator has control of each part of the process.

I work in process control, not discrete manufacturing.

On my systems Auto is fully automatic, with operating targets and starting and flow control valves etc. controlled by the process sensors.

In Manual starting and flow targets and so on are set by the operator. However, machine protection and operator protection is still enabled, and operating targets set by the operator are clamped at the safe operating range if how he tries to manipulate them to improper settings.

There are some machines which should NEVER have manual controls. We have 14 hydraulic presses which have no manual controls whatsoever for safety reasons. The operator's sole controls are START (two hand), ABORT, and OPEN. Under no circumstance would an operator be trusted to perform any press motion sequences in manual, nor could he possibly react fast enough. In implementing manual controls all safety aspects and threats must be throughly evaluated.

Thank goodness for HMIs
We have converted most of our hardwired, selector switch inputs to HMI inputs and I have found sometimes we have many types of Auto and Manual modes. But generally I agree that the term Auto indicates that the PLC is deciding and Manual is that the operator is making some of the control decisions.
By the way, is the word MANual politically incorrect?
ManMachineInterface became HumanMachineInterface so it follows
that we should call operator control HUMANual!
Brian.

Sliver said:

By the way, is the word MANual politically incorrect?

Click to expand...

That might be the reason so often the switch is labeled HAND-AUTO.

On Most Of Our Indexing Machines We Tend To Use Run/safe/jog
Run Beign Auto (one Input), Jog Beign Manual (another Input) And Safe Both Disabled.
Usually Done With A Key Switch So In Safe The Key Can Be Removed And Retained By The Person Working On The Machine.
The Auto Manual As Described In The First Post Sounds Like Run And Step Of A Program To Me

Seems like another area where many of us do it a little diiferent from everyone else.

kind of like, MCR's, e-stops,etc.

I like to feed the auto, manual, start, and stopp buttons as inputs, and use simple ladder logic, even on engine gerator controls.

sometimes makes it easier when dealing with electricians with very basic skills.

regards.....casey

hi,
Well, in some case it is all at the end of what the user or buyer wants. Here we are working and making the projects for an end user.
We can give our oppinion, but at the end it must work in the way they want it, and not in the way we wanted (not discussing here the safeties of the machine, that must be taken in account by both sides).
Also, the pass between manual and auto and viceversa, is according to their taste. I made once a control that when you make the pass from one to the other, it didn't change anything, only the abilitie of the operator to touch some parameters. and I also have to program one that when you make a switch, it stopped all the machine.
Like I said previously... its what they wanted.