First decide one thing: is this one extra feature, or a different machine?
When a manufacturer sends in a chair with a standing function or a seat-elevation function, the opening line is usually "it is the same as our standard model, there is just one extra standing action." For test planning purposes that statement does not hold up. There is a single criterion to apply: during use, does this mechanism change the position of the centre of gravity, change the support polygon, or change the number of postures in which the occupant can remain? If any one of those is changed, the stability, strength and control-related judgements can no longer be covered by running the chair once in the seated posture. They have to be worked through separately for every posture the occupant can stop in.
That criterion drives the entire workload downstream. Get it wrong at the planning stage and the price is rescheduling after the sample lands, reissuing the posture-locking documentation, reconfiguring the loading. Get it right at the planning stage and the cost is close to zero. It is exactly why we push for a planning meeting before the structure is frozen, rather than waiting until the sample has been crated.
Three dimensions decide how many items get added
| Decision point | Situation | How it is handled |
|---|---|---|
| Are postures continuously stoppable | Only two mechanically locked detents, seated and standing | Evaluate the two end postures separately; treat the transition between them as an action-safety question |
| Are postures continuously stoppable | Infinitely adjustable, the occupant can stop at any angle | Take envelope postures within the declared range and add judgements covering the transition itself |
| Is the drive interlocked when standing | Driving is electrically or mechanically inhibited while standing | Drive-related dynamic judgements may be confined to the seated posture, but the interlock itself needs its own failure-mode verification |
| Is the drive interlocked when standing | Driving is permitted while standing or part-standing | Dynamic stability, braking and obstacle-negotiation judgements have to be repeated in the standing posture |
| Is the lift loaded | Unloaded lift, the occupant has to transfer first | Mechanism strength can be considered under unloaded application, but protection against misoperation still has to be verified |
| Is the lift loaded | The occupant is raised while seated | Mechanism strength, protection against unintended descent and posture retention on loss of power all become mandatory |
| Power source | Manual hydraulic or mechanically assisted | Emphasis falls on operating forces, locking reliability and return control |
| Power source | Electrically driven | Add verification of posture behaviour under controller fault conditions |
Walk down this table row by row in the planning meeting and the item list is essentially framed. Our experience is that manufacturers tend to think only about "can it stand up without tipping over," whereas the questions that actually consume plan time are "what happens if power is lost halfway up" and "what happens if the joystick gets knocked while standing."
Stability: evaluated posture by posture, not product by product
Static stability is run to the method of ISO 7176-1 and dynamic stability to the method of ISO 7176-2. For a conventional wheelchair each of those is one pass and the matter is closed. For standing and lifting products it is not.
Three points matter here.
First, the object of evaluation shifts from "one chair" to "several states of one chair." The seated posture, the fully standing posture, the fully raised posture, and — for infinitely adjustable products — the intermediate envelope postures taken within the declared range are each an independent object of evaluation. Which posture is the most tip-prone cannot be settled by intuition; it has to be measured. On a fair number of products the centre of gravity actually falls back once standing is complete, and the genuinely unfavourable condition is some intermediate position during the rise. Test only the two end points and that position gets missed.
Second, each posture needs a defined locking method and a state indication. The test engineer has to be able to hold the sample stably in the posture being evaluated, and that posture has to be one the occupant can genuinely remain in during real use. If the manufacturer cannot state which postures are permitted for remaining in, there is no baseline for the judgement and the plan goes back.
Third, ballast and restraint arrangements have to match the posture. Load distribution in the standing posture is nothing like the seated posture, so the point of application of the test load and the way restraint straps are used both have to be written into the plan and fixed there. Otherwise repeat tests on different batches are not comparable and the reports cannot corroborate one another.
Strength, impact and fatigue: what is new is the mechanism itself
When strength, impact and fatigue are assessed to the methods of ISO 7176-8, a conventional wheelchair puts the attention on the frame, forks, footrests and armrests. Standing and lifting products additionally have to bring the mechanism itself into the load path: the joint between the lift column and the seat frame, the pivot pins of a scissor mechanism, the support points of the knee pad and chest pad in the standing posture, and the transition welds or bolt groups between the mechanism and the main frame.
The test for inclusion is one sentence: in the new posture, does this location carry a load the original design never gave it? If it does, it needs separate consideration. If it merely follows the motion without carrying load, it can be handled as an existing component. We suggest the manufacturer's structural engineer produce a load-path diagram at the planning stage, marking the direction in which the new loads travel. It is far less trouble than adding tests after the fact.
Another point that routinely gets overlooked is posture selection for cyclic loading. Mechanism fatigue should not be run only in the stowed state. The stowed state is usually the low-stress state, and a cyclic loading run completed there produces a conclusion with little bearing on actual use. The loading posture has to line up with the high-load conditions identified in the risk file.
The risk management file belongs ahead of the test plan
The test plan for a standing or lifting product is, in substance, reverse-engineered from the hazard list. If the risk management file built to ISO 14971 has not taken shape by the time the sample is submitted, the planning meeting turns into the test engineer guessing hazards on the manufacturer's behalf. That is slow, and it leaves gaps.
These products have a handful of recurring hazards. Anything absent from the risk file will certainly be raised in the planning meeting:
- Pinch and shear locations within the moving mechanism, particularly where a scissor mechanism interacts with the footplate linkage
- Posture retention on loss of power, loss of pressure or controller fault, and whether unintended descent is possible
- Failure of the restraint system in the standing posture, and the consequences of failure of the knee pad, chest pad or belt individually
- Failure of the interlock logic between drive and posture
- Misoperation paths in the two separate scenarios of occupant operation and attendant operation
- Initiating the standing action on a slope or on uneven ground
Write these into the risk file, derive the verification items from the risk file, and the test plan has a documented basis. Do it the other way round — test first, write the risk file afterwards — and you usually find the items tested do not correspond to the hazards identified, which means another round.
Mapping to submissions for the domestic market
For the Chinese market, the GB/T 18029 series is applied by the corresponding parts, to be confirmed against the current valid version of the standard text. Two practical points. First, the correspondence between the domestic parts and the international methods has to be written out item by item in the plan; do not wave it through with a blanket statement about identical adoption. Second, standing and lifting are additional functions, and some judgements have no directly corresponding clause in the general parts. Where that happens, describe the basis of evaluation in narrative form and state the source of the method clearly in the report.
If the product is heading for more than one market, define the posture states, load configuration and sample configuration consistently within a single test campaign, so the same sample is not described as being in different states across different reports. For an overview of the standards frameworks that apply to different markets, start with the standards basis summary.
Pre-submission self-check list
| Check item | Passing condition | What happens if you skip it |
|---|---|---|
| List of stoppable postures | All permitted resting postures and their locking methods stated in writing | No baseline for stability judgements; the plan goes back |
| Posture and drive interlock statement | States which postures permit driving and how the interlock works | Scope of the dynamic items cannot be settled |
| Load-path diagram | Marks the load-bearing locations of the new mechanism and the direction of transfer | Strength and fatigue items are easy to miss |
| Loss-of-power behaviour statement | Describes posture retention or controlled descent after power loss | Verification has to be added on site; schedule slips |
| Risk management file | Covers pinch points, unintended descent and restraint failure | Planning meetings go in circles; progress becomes unpredictable |
| Frozen sample configuration | The submitted configuration matches the submission dossier | Report and product do not match; the report has to be reissued |
| Draft instructions for use | Includes posture usage limits and prohibited scenarios | Some judgements lack supporting documentation |
| Control location statement | Reachability of each control in the standing posture | Misoperation paths cannot be evaluated |
Three approaches that genuinely cost you
First, submitting a single sample locked in the seated posture. If the posture cannot be changed on site, every posture-related item is void and the whole thing gets rescheduled. Fixing this at the planning stage is free; fixing it once the sample has arrived means queueing again.
Second, instructions for use that say nothing about prohibiting the standing action on a slope, while the risk file lists exactly that as a control measure. The two documents contradict each other, the report cannot be issued, and everything waits for the manufacturer to update the instructions and for the cross-check to be repeated. One round of that usually takes longer than the testing did.
Third, changing the lift mechanism supplier midstream while continuing to rely on the original report. The mechanism is a load-bearing part, so a change of supplier is a change affecting the load path, the original report does not cover it, and the strength and stability items normally have to be run again. This shows up constantly during production ramp-up, where component sourcing and regulatory documentation are not linked, and the problem surfaces only at review time.
Stair-climbing products and the lifting discussed here are two different things; their judgement logic follows its own rules, so do not transplant the posture criteria in this article directly onto them. For the difference in baseline items between manual and powered chairs, see manual wheelchair testing and powered wheelchair testing respectively. For the distribution of project types we have completed, see project cases.
It should be noted that a laboratory accreditation mark only attests that the laboratory holds the corresponding technical competence within its accredited scope. It is not a commitment as to the market access outcome in any target market. Whether a plan passes on the first attempt depends on the state of the product, the completeness of the documentation and the declared scope itself.
Lock the plan before the structure is frozen
We provide third-party testing for wheelchairs and mobility aids from laboratories in Shanghai and Hefei, accredited by CNAS, CMA and IAS (USA). For products carrying an additional mechanism such as standing or seat elevation, our advice is to walk through the posture list, load configuration and sample configuration before the structural design is frozen. It is far less trouble than adjusting after the sample arrives. To confirm an item list or discuss scheduling, call +86 132 4819 8029 directly, or request a quote describing the product form and target market. We will return the corresponding item list and sample preparation requirements against your declared scope.